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HOW TO CONTROL 

PLANT DISEASES 



MALCOLM C. SHURTLEFF 




Florida Agricultural 
Experiment Station Library 

Gainesville, Florida 



■ 





How To Control 

PLANT DISEASES 

in Home and Garden 



-4 



HOW TO CONTROL 

PLANT DISEASES 

in Home and Garden 
MALCOLM C. SHLIRTLEFF 

Associate Professor of Plant Pathology 

and Extension Plant Pathologist, 

University of Illinois 

formerly Extension Plant Pathologist, 

Iowa State University 

Art Work by 
ROGER D. ALBERTSON 













' 












: 




The Iowa State University Press 

^JtmeSj IOWA, U.S.A. 



- ! i. 



tarn- 

CULTURAL 
UBRARY 



© 1962 The Iowa State University Press. 
All rights reserved. 

Composed and printed at the 
Iowa State University Press, 
Ames, Iowa, U.S.A. 



Library of Congress catalog card number: 62-9120 



CONTENTS 



^ 



t 

\ 



See detailed Table of Contents at beginning of 
each section 



Color Code Page 
Section 1 

INTRODUCTION (Brown) 1 

Section 2 

"WHAT IS IT?" (Red) 13 

Environmental Factors 14 

General Diseases 33 

A. Foliage Diseases 33 

B. Stem Diseases 62 

C. Flower and Fruit Diseases 70 

D. Root and Bulb (Corm) Diseases 73 

E. Parasitic Flowering Plants 78 

Section 3 

"WHAT CAN I DO ABOUT IT?" .... (Green) 81 

Measures 82 

Materials 84 

Equipment 92 

Section 4 
HOME AND GARDEN PLANTS AND THEIR DISEASES .107 

Other Useful Information 

APPENDIX 417 

GLOSSARY 447 

INDEX 463 



</W/ 



A NOTE TO THE READER 



All living plants grown in and around the home, yard, and garden 
are subject to attack by disease-producing organisms and agents. Plant 
diseases — the despair of gardeners the world over — should be con- 
sidered as much a part of nature as sun, wind, rain, weeds, and insects. 

This book is intended to acquaint gardeners — amateur and pro- 
fessional alike, as well as the many people who advise them — with 
the numerous types of disease problems that flowers, vines, trees, 
shrubs, lawngrasses, vegetables, and fruit may contract. The cultural 
and chemical practices necessary to keep them in check are outlined. 
Naturally a book of this size cannot exhaust the subject of more than 
50,000 diseases. But it does describe the diseases — common and un- 
common — of more than 810 genera of home and garden plants grown 
in the United States and Canada. Ailments of the same plant which 
look much alike have often been lumped together. Closely related 
plants which are damaged by the same general group of diseases, like 
those in the cabbage, cucumber, and carnation families, are also placed 
together. Since all plants are listed by both common and scientific 
names, you as a reader and user should have little difficulty finding 
what you are looking for. 

To cover as much material as possible in a brief space, the style is 
terse and pointed. The material has been organized into sections 
which are coded with different colors. Each section has its own index. 
Each is a unit by itself and should answer such questions as "What is 
it?" "What can I do about it?" and "How serious is it?" 

Do not expect this book to be a panacea for all your garden ills. 
Occasionally diseases are found which can be easily confused with 
other diseases, soil deficiencies, insects, or mechanical injury. In cases 
like this, check over the disease descriptions given under the specific 
plant in Section 4 and under the disease in Section 2. Think back over 
the past history of the plant and the area of the yard or garden where 
it is growing. Still no answer? Now it's time to call in a specialist for 
his evaluation. Don't be afraid to talk over your problem with a suc- 
cessful grower, your local nurseryman, florist, or the people at the 
garden supply center. Ask them for their advice. There is also the 
local county extension office or extension specialist at your land-grant 
college or university whom you can call on for assistance. 

[vii] 



viii A NOTE TO THE READER 

No attempt has been made to include insect injuries except in a 
few instances when the effects of such injuries lead to definite disease- 
like conditions. Where insects are important in transmitting disease- 
producing organisms and agents, control measures are suggested. 

Intentionally, I have avoided use of scientific names for the causal 
pathogens and agents. Common names generally suffice and are much 
more meaningful to all (except a handful of biologists) than is 
Colletotrichum lindemuthianum , Gymnosporangium juniperi-virgin- 
ianae, or Belonolaimus longicaudatus. Besides, common names usually 
lend stability to nomenclature. The scientific names of many bacteria, 
viruses, and nematodes, particularly, are in a state of flux. 

Use this book as a handy reference when you're in trouble. Or, 
better still, before you're in trouble. And remember that even the best 
gardeners occasionally have disease problems. 

Before plunging in, read the "How to use this book" section. From 
then on we hope it will be clear sailing. 

ACKNOWLEDGMENTS 

No book containing the condensate from the research findings of 
thousands of plant scientists can possibly be the work of one person. 
I am greatly indebted to the following: George Rose and Marshall 
Townsend helped with organization and general layout; Betty Rinder- 
knecht gave the text short, punchy sentences and provided prelim- 
inary editorial help; Ray Fassel was a genial and painstaking editor; 
the great majority of the illustrations were done by a brilliant young 
artist, Roger D. Albertson; Mrs. Betty Lartius contributed five sketches 
in Section 1; photographs were kindly provided by friends and by 
chemical or equipment manufacturers with credit for these being given 
in the legends to the figures; John L. Weihing, Charles H. Sherwood 
and Don C. Norton were kind enough to read the entire manuscript 
in an early stage and contributed many valuable comments and 
criticisms; A. E. Cott, James C. Horton, John P. Mahlstede, Harold S. 
McNabb, Jr., Lawrence I. Miller, Ben F. Vance, and Donald B. White 
critically read certain parts of the manuscript; Mrs. Connie Betten 
and my wife, Margaret, assisted in the typing. My wife also had the 
task of taking care of our three children while the manuscript was 
being prepared and later typed. This book could not have been written 
without the generous assistance of these people. 

In making these acknowledgments, I wish to make it clear that 
those who have assisted are absolved from any responsibility for errors 
or mistakes I have committed, in spite of their efforts. 

Malcolm C. Shurtleff 

January, 1962 



SECTION 1 



Introduction 



How to use this book .... 

Where you can get additional 
help 

Land-grant institutions and agri- 
cultural experiment stations in 
the United States 

How to send in plant specimens 

Extent of plant diseases . . . 



1 What is a plant disease? ... 6 

Classification of diseases ... 6 

3 Causes of plant diseases ... 7 
Unfavorable growing conditions 7 
Bacteria 8 

4 Fungi 9 

5 Viruses 10 

6 Nematodes 11 



HOW TO USE THIS BOOK 



This book is written primarily for the 
home gardener. It also should prove a use- 
ful reference for the commercial vege- 
table grower, orchardist, berry grower, 
nurseryman, turf specialist, student or ex- 
tension specialist in the plant sciences, 
county agricultural agent, vocational ag- 
riculture teacher, specialist for commer- 
cial concerns or state departments of ag- 
riculture, garden writer, and others who 
know and love plants. 

The attempt has been to write in easy- 
to-understand language, omitting as much 
technical terminology (e.g., scientific 
names of disease-causing organisms, myco- 
logical or pathological terms) as practi- 
cal. An extensive glossary (pages 447-61) 
explains the technical terms used in the 
text. 

Two questions people invariably ask 
about a plant disease are, "What is it?" 
and "What should I do about it?" Some- 
times such questions as "How serious is 



it?" or "Will it kill my plants?" follow. 
This book answers these four basic ques- 
tions. 

The answer to "What is it?" or disease 
diagnosis is based on plant responses 
which are expressed as symptoms. These 
result from some disease-inducing factor. 
The most general types of diseases, based 
on external and internal symptoms, are 
given in Section 2 (red pages) . The 
listings of Plants Attacked in this section 
come largely from USDA Handbook No. 
165, Index of Plant Diseases in the United 
States, and the second edition of Cynthia 
Westcott's Plant Disease Handbook pub- 
lished by the D. Van Nostrand Company, 
Inc. 

Section 3, "What Can I Do About It?" 
(green pages) covers the essential points 
in control which govern most plant dis- 
eases. Usually several types of control 
measures are needed to protect against, 
check, or eradicate an infection. The 



[1 ] 



HOW TO USE THIS BOOK 



amount of disease control is dependent 
upon the timeliness, completeness, and 
type of control measures used. 

Cross references are made to general 
types of diseases pictured and described 
in Section 2, and to control measures out- 
lined in Section 3, listed under individual 
plants, or given in the Appendix. 

The information found in Section 4 
(pages 107-415) includes those trees, 
shrubs, vines, house plants, flowers, fruit, 
vegetables, and lawngrasses likely to be 
grown in and around the home, yard, and 
garden in any geographical area of the 
United States. Certain native plants some- 
times grown in wild gardens are listed as 
well as forest trees which are sometimes 
used as ornamentals. Strictly field crops 
have been omitted. 

The plants are listed alphabetically 
from Aaronsbeard to Zygopetalum under 
both common and scientific names. The 
important diseases are listed under each 
plant. To reduce bulkiness, plants have 
been put together which have similar 
disease problems. Where practical, all 
members of a plant family are placed un- 
der one or several plants in that family. 

For example, plants related to carna- 
tion, e.g., garden pinks, sweet-william, 
babysbreath, Maltese cross, catchfly, and 
others in the family Caryophyllaceae hav- 
ing economic value are put together un- 
der carnation (see example below) , prob- 
ably the best known member of the fam- 
ily. Plants listed with carnation are cross- 
indexed under both common (Maltese 
cross) and scientific (Lychnis) names and 
refer you to carnation. 

Where several species or horticultural 
types of a genus are widely grown, e.g., 
cottage, grass, maiden, and rainbow gar- 
den pinks, these are listed alphabetically 
within brackets after GARDEN PINKS 
(see below) . Members of a plant family 
are listed alphabetically by the scientific 
name of the genus after the first common 
name (CARNATION) . Agrostemma 
comes before Arenaria with the remaining 
genera Gypsophila, Lychnis, Plumaris, 
and Silene following. 

Example: 
CARNATION [FLORIST'S, HARDY], 
GARDEN PINKS [ COTTAGE, GRASS, 

MAIDEN, RAINBOW], SWEET- 
WILLIAM (Dianthus); CORNCOCKLE 



(Agrostemma); SANDWORT (Arenaria); 
BABYSBREATH (Gypsophila); 
EVENING CAMPION, MULLEIN- 
PINK, MALTESE CROSS, RED and 
ROSE CAMPION, JERUSALEM-CROSS, 
ROSE-OF-HEAVEN (Lychnis); HARDY 
GRASS PINK (Plumaris); CUSHION- 
PINK, FIRE-PINK, STARRY and MOSS 
CAMPION, CATCHFLY [ALPINE, 
SWEET-WILLIAM ] (Silene) 

Where a disease infects certain plants in 
a listing and not others, the plants at- 
tacked are listed in parentheses after the 
name of the disease. Following the carna- 
tion example above we find on pages 169 
that Fusarium Wilts infect carnation, 
pinks, and sweet-william; Bacterial and 
Verticillium Wilts attack only carnation; 
while Alternaria Leaf Spot and Branch 
Rot infect carnation, Maltese cross, pinks, 
and sweet-william. 

The diseases listed in this book are 
those reported from the continental 
United States. Diseases peculiar to Ha- 
waii, Alaska, Puerto Rico, the Virgin Is- 
lands, and the Canal Zone are omitted 
principally for lack of space. Many of 
the diseases are found more or less gen- 
erally throughout the world. 

The geographic range, in nature or in 
cultivation, of the various diseases should 
be taken only as a rough guide. Diseases 
listed as "General" are usually coexten- 
sive with the plant host; "Widespread" 
means that the disease is reported from 
many scattered locations in the United 
States but is not prevalent; "Frequent" 
and "Occasional" denote intensity as well 
as range of occurrence. 

Certain regional designations (e.g., east- 
ern, southern, or southeastern states; Pa- 
cific Coast, Midwest) are also used to de- 
note specific geographical areas where cer- 
tain diseases are prevalent or have been 
reported. 

If appropriate, the prevalence of the 
disease, the potential destructiveness of 
the ailment, and the weather conditions 
which favor or check disease development 
are mentioned. This should answer the 
questions "How serious is it?" and "Will 
it kill my plant?" 

The information you seek should be 
easy to find, especially with the use of the 
extensive index. 

The Appendix (pages 417-46) contains 



WHERE YOU CAN GET ADDITIONAL HELP 



average spray programs for common fruits 
and seed and soil treatments with meth- 
ods, materials, and precautions. Also in- 
cluded are conversion tables for measur- 
ing dry and liquid chemicals, useful units 
of measure, methods for converting Fahr- 
enheit to Centigrade and vice versa, 
measurements and rates of application 
equivalents, a pesticide compatibility 
chart, and an operating chart for tractor 
boom sprayers. 

To illustrate, let us take a plant disease 
and find all we can regarding it. To make 
the case specific, suppose the apple tree in 
the back yard that for so long has granted 
shade and fruit in season, this year has 
alarming spots on its leaves, and, as the 
fruit matures, spots which are somewhat 
similar to those on the leaves appear on 
the fruit as well. A neighbor spoke of vari- 
ous apple diseases to you at the time you 
purchased the tree and you vaguely re- 
member his mentioning that a disease 
that sounded like skob or scab might pro- 
duce the symptoms that are evident. 

So you begin in Section 2 looking un- 



der disease (14) Scab. After reading the 
introductory material about it, you come 
to the material on control and observe 
that a spray program is suggested. Section 
4 presents plants in alphabetical order, so 
looking through the A's you come to 
apple. Here disease 2 is Scab and controls 
are mentioned under it. 

On the other hand, it is possible that 
you only know that it is a disease of apple 
since it is on your apple tree. In that 
case, you would immediately turn to the 
information on apples in Section 4 and 
start comparing your diseased specimen 
with the explanations and illustrations 
presented there for identification of the 
disease. Once the evidence indicates that 
the disease is scab, you will turn back to 
Section 2 and read the material there on 
scab as well as reading that in Section 
4 and also turn to Section 5, the Appen- 
dix, to check the apple spray program. 
From this point on, it is only necessary to 
follow the directions and observe the 
suggestions given in the various parts of 
the book to which you are directed. 



WHERE YOU CAN GET ADDITIONAL HELP 



You can get help on diagnosis and con- 
trol of plant problems by contacting your 
county agricultural agent (sometimes 
called farm advisor, county agent, or 
county extension director) or by writing 
your state land-grant college or univer- 
sity. A listing of these institutions is be- 
low. Write to your extension plant path- 
ologist concerning diseases, the extension 
entomologist for information about in- 
sects, or to the extension horticulturist 
regarding cultural problems. 

All states publish free pest control 



recommendations. Each state department 
of agriculture along with the USDA have 
a wide variety of printed matter on plant 
pest control which is available through 
your county extension office or land-grant 
institution. 

There are local authorities or plant 
experts in your community who would 
be only too happy to talk with you about 
your disease problems. These people in- 
clude your florist, nurseryman, garden 
supply dealer, commercial fruit and vege- 
table growers, and turf specialist. 



LAND-GRANT INSTITUTIONS AND EXPERIMENT STATIONS 

LAND-GRANT INSTITUTIONS AND AGRICULTURAL 
EXPERIMENT STATIONS IN THE UNITED STATES 



All states have at least one Extension 
Horticulturist to answer questions on 
cultural management of garden plants. 
States listed below with one asterisk (*) 
have an Extension Entomologist (insects, 
mites, rodents) and states with two aster- 
isks (**) also have an Extension Plant 
Pathologist (diseases) . Write to the 
specialist in care of the College of Agri- 
culture at your state land-grant institu- 
tion. 

For free bulletins, circulars, pamphlets, 
spray schedules, etc., write to the Bulletin 
Room, College of Agriculture, at your 
state university or college. 

* Alabama: Alabama Polytechnic Insti- 
tute, Auburn. 

** Alaska: University of Alaska, College 
(or Experiment Station, Palmer) . 

** Arizona: University of Arizona, Tuc- 
son. 

** Arkansas: University of Arkansas, Fay- 
etteville (or Cooperative Extension 
Service, 1201 McAlmont Ave., Little 
Rock) . 

** California: University of California, 
Berkeley 4; Agricultural Extension 
Building, Riverside, or Davis. 

* Connecticut: University of Connecti- 
cut, Storrs (or Connecticut Agricul- 
tural Experiment Station, New Haven 
4). 

** Delaware: University of Delaware, 
Newark. 

** Florida: University of Florida, Gaines- 
ville. 

* Georgia: University of Georgia, Ath- 
ens [ or Agricultural Experiment Sta- 
tion (State) , Experiment; Coastal 
Plain Station, Tifton ]. 

Hawaii: University of Hawaii, Hono- 
lulu 14. 

** Idaho: University of Idaho, Extension 
Service, Boise; Agricultural Experi- 
ment Station, Moscow. 

** Illinois: University of Illinois, Ur- 
bana. 






Indiana: Purdue University, Lafay- 
ette. 

Iowa: Iowa State University, Ames. 

Kansas: Kansas State University, Man- 
hattan. 

Kentucky: University of Kentucky, 
Lexington 29. 

Louisiana: Louisiana State University, 
University Station, Baton Rouge 3. 

Maine: University of Maine, Orono. 

Maryland: University of Maryland, 
College Park. 

Massachusetts: University of Massa- 
chusetts, Amherst. 

Michigan: Michigan State University, 
East Lansing. 

Minnesota: Institute of Agriculture, 
University of Minnesota, St. Paul 1. 

Mississippi: Mississippi State Univer- 
sity, State College. 

Missouri: University of Missouri, Co- 
lumbia. 

Montana: Montana State College, 
Bozeman. 

Nebraska: College of Agriculture, 
University of Nebraska, Lincoln (or 
Scott's Bluff Experiment Station, 
Mitchell) . 

Nevada: University of Nevada, Reno. 

New Hampshire: University of New 
Hampshire, Durham. 

New Jersey: State College of Agricul- 
ture, Rutgers University, New Bruns- 
wick. 

New Mexico: New Mexico State Uni- 
versity, University Park. 

New York: New York State College of 
Agriculture, Cornell University, Ithaca 
(or Agricultural Experiment Station, 
Geneva; Ornamentals Research Lab- 
oratory, Farmingdale) . 

North Carolina: North Carolina State 
College, State College Station, Raleigh 
(or A.&T. College, P.O. Box 1014, 
Greensboro) . 



HOW TO SEND IN PLANT SPECIMENS 



North Dakota: North Dakota State 
University, State College Station, Far- 
go. 

Ohio: The Ohio State University, Co- 
lumbus 10 (or Agricultural Experi- 
ment Station, Wooster) . 

Oklahoma: Oklahoma State Univer- 
sity, Stillwater. 

Oregon: Oregon State University, Cor- 
vallis. 

Pennsylvania: The Pennsylvania State 
University, University Park. 

Puerto Rico: University of Puerto 
Rico, Rio Piedras. 

Rhode Island: University of Rhode 
Island, Kingston. 

South Carolina: Clemson Agricultural 
College, Clemson. 

South Dakota: South Dakota State 
College, Brookings. 

Tennessee: University of Tennessee, 
Knoxville 16. 

Texas: Texas A.&M. College, College 
Station (or Box 476, Weslaco; Tyler 
Experiment Station No. 2. R. 6, Tyler; 



Agricultural Building, Texas Tech., 
Lubbock) . 

* Utah: Utah State University, Logan. 

* Vermont: University of Vermont, Bur- 
lington. 

Virgin Islands: Virgin Islands Agric. 
Project, Kingshill, St. Croix (officer in 
charge) . 

** Virginia: Virginia Polytechnic Insti- 
tute, Blacksburg [or Virginia Truck 
Experiment Station (truck crops) , 
Norfolk 1; Piedmont Fruit Research 
Laboratory, Charlottesville; Winches- 
ter Fruit Research Laboratory, Win- 
chester ]. 

** Washington: Washington State Uni- 
versity, Pullman (or Western Wash- 
ington Experiment Station, Puyallup) . 

** West Virginia: West Virginia Univer- 
sity, Morgantown. 

** Wisconsin: University of Wisconsin, 
Madison 7 (or Peninsular Branch Ex- 
periment Station, Sturgeon Bay) . 



Wyoming: 
Laramie. 



University of Wyoming, 



HOW TO SEND IN PLANT SPECIMENS 



To help in diagnosing plant pests (dis- 
eases, insects, or weeds) , wrap fresh plant 
specimens, showing a range of symptoms, 
in cellophane, plastic bags, wax paper, or 
aluminum foil. Do not send fleshy fruit 
in advanced stages of decay. Seal the 
wrapper tightly and mail in a crush-proof 
carton or mailing tube. Do not add mois- 
ture. Enclose or attach a letter giving as 
much history as possible. This should in- 
clude the date collected, variety and kind 



of plant attacked, prevalence of the pest, 
degree of severity, description of the pest, 
part diseased or injured, extent of garden 
area involved, cropping history when 
known, weather and soil conditions, re- 
cent fertilization, watering, pest control 
measures, etc. Don't forget your return 
address! Remember that correct diagnosis 
is essential before control measures can 
be suggested. A diagnosis can only be as 
good as the specimen you send! 



EXTENT OF PLANT DISEASES 



EXTENT OF PLANT DISEASES 



All garden plants are attacked at one 
time or another by disease. There are 
over 80,000 different diseases. In addi- 
tion several hundred species of parasitic 
nematodes also injure plants. 

The annual loss in the United States 
from plant diseases and nematodes is 
about $4 billion. This loss means higher 
grocery bills plus increased costs for 
clothing and shelter for all of us. Did 
you know, for example, that diseases 
cause more loss to our nation's forests 
each year than does fire? 

Plant diseases are a normal part of 
nature and can be considered as one of 
the many environmental factors that help 
keep each of the many thousands of liv- 
ing organisms in balance with each other 
in undisturbed nature. When man selects 
and cultivates plants he must recognize 



that diseases will have to be considered 
as one of the many expected hazards. 

Plant diseases are not new. They un- 
doubtedly arose and developed as life 
arose and developed on earth. The Bible 
mentions many injurious pests including 
rusts, mildew, and blast. These diseases 
and others have plagued man and caused 
famines since the dawn of recorded his- 
tory. Fossils have been found which sug- 
gest that plants had disease enemies long 
before man even appeared on earth. 

This book is not designed to scare you 
about the thousands of diseases you will 
never see in a garden. It is to enable 
you to know and recognize the occa- 
sional disease which may require prompt 
action. The pictures and disease descrip- 
tions should help you become familiar 
with the most common ones. 



WHAT IS A PLANT DISEASE? 



When a plant is continuously affected 
by some factor which interferes with its 
normal structure or activities, it is said 
to be diseased. Injury, in contrast, re- 
sults from a momentary damage. Broad- 



ly speaking, a plant is considered diseased 
when it does not develop or produce nor- 
mally, considering the conditions of its 
growth. Often there is no sharp distinc- 
tion between healthy and diseased plants. 



CLASSIFICATION OF DISEASES 



A sick plant may not be as different 
from a sick human or animal as you 
think. For instance, increases in tempera- 
ture and rate of respiration may occur 
when plants become infected. 

Plant ailments, like those of humans or 
animals, are often classified by their effects 
or visible symptoms. Humans have fevers 
and plants have wilts. People suffer from 
colds, sore backs, an unbalanced diet, or 
measles while plants are weakened with 
spots, blights, rots, mildews, cankers and 
rusts, or an unfertile, compacted soil. 

Many plant diseases, however, which 
appear alike by external symptoms may 
be caused by widely different micro-organ- 



isms or agents and require completely 
different methods of control. This is 
where a careful laboratory diagnosis by a 
trained plant doctor comes in handy. It is 
obvious that the causal organism, agent, 
or environmental factor be known posi- 
tively before proper control measures can 
be initiated. 

In Section 2 "What is it?," we have 
classified plant diseases by symptoms 
divided up conveniently into those which 
affect the foliage; stems, twigs, branches, 
or trunk; the flowers and fruits; or the 
roots and other underground parts. 

Plant diseases may also be grouped ac- 
cording to their causes. 



CAUSES OF DISEASES 



CAUSES OF PLANT DISEASES 



The causes of plant diseases may con- 
veniently be divided into two groups: 
those caused by unfavorable growing con- 
ditions (nonparasitic) and those caused 
by a parasite (bacteria, fungi, viruses, 



nematodes, and parasitic flowering plants). 
Unfavorable growing conditions. Non- 
parasitic or noninfectious diseases include 
those caused by excesses or deficiencies of 
light, air humidity, water, or essential 




1. Nonparasitic diseases. A. Sunscald and blossom-end rot of tomato, B. Leaf scorch 
of maple, C. Boron deficiency of beet, D. 2,4-D injury to redbud leaves. 



8 



CAUSES OF DISEASES 



soil nutrients (e.g., nitrogen, phosphorus, 
potassium, calcium, iron, magnesium, 
manganese, boron, copper, molybdenum, 
zinc, sulfur, etc.) , soil moisture-oxygen 
disturbances, extreme acidity or alkalin- 
ity in the growing medium, pesticide in- 
jury, extremely high or low temperatures, 
injurious impurities in the air or soil, soil 
grade changes, girdling tree roots, 
mechanical and electrical agents, plus un- 
favorable preharvest and storage condi- 
tions for fruits, vegetables, bulbs, etc. 
Plants in poor health from unfavorable 
growing conditions outnumber those 
caused by disease-producing organisms. 

This book doesn't attempt to cover in 
detail the wide range of nonparasitic 
ailments which affect garden plants. We 
simply suggest you follow the best cul- 
tural practices for each of your garden 
plants as given in state and federal gar- 
den bulletins, nursery and seed catalogs, 
books and magazines. This would include 
information on varieties to plant, plant- 
ing depth, shade or sun, type of soil, 
fertilization programs, water require- 



ments, winter or summer protection, 
pruning, insect control, weed control, 
and other practices. Some general in- 
formation on plant culture in relation 
to plant diseases is given in Section 2. 
Additional help may be obtained by 
talking with experienced and reliable 
garden supply dealers, nurserymen, flo- 
rists, arborists, or fellow gardeners in your 
community. Garden clubs and plant so- 
cieties also offer a means of exchanging 
helpful gardening hints. 

Several of the more common nonpara- 
sitic diseases are shown in Figure 1. 

Parasites. The diseases we shall concern 
ourselves with primarily are those caused 
by microorganisms (bacteria, fungi, and 
nematodes) and viruses. These are infec- 
tious diseases which often spread easily 
from diseased to healthy plants. 

Bacteria. Bacteria are minute, one- 
celled plants (although recent staining 
techniques have shown that the bacterial 
body may actually be composed of 2 to 
4 cells) which lack chlorophyll and 
hence cannot make their own food. 




Fig- 



2. Bacteria. A. Different forms as you might see them under a powerful laboratory 
microscope, B. Bacteria showing various types of flagella. 



CAUSES OF DISEASES 



Placed end to end it would take about 
20,000 bacteria to make an inch. Twenty 
trillion bacteria may weigh only an 
ounce. Yet the top foot of soil in 1,000 
square feet of your garden contains about 
20 pounds of bacteria! A cubic foot of 
garden soil weighs an average of 85 to 
90 pounds. 

Bacteria multiply simply by dividing in 
half every 20 minutes to an hour or more 
when conditions are favorable. If a single 
bacterium divided in half and, if all of 
its descendents did likewise every hour 
for a day, there would be nearly 
17,000,000 bacteria after just 24 hours. 
Is it any wonder that bacteria cause iris, 
calla, vegetables, and fruits to sometimes 
rot so quickly? 

Bacteria enter plants through wounds 
and small natural openings that occur 
over the surface of plants. Once bacteria 
are inside a plant they multiply rapidly, 
break down tissue, and often migrate 
throughout the plant. Many types swim 
about in water or in plant sap by means 
of whipping one or more "tails" called 
flagella (Figure 2) or by a rhythmic pul- 
sation of the bacterial body. 

Bacteria are spread by man through 
cultivating, pruning, and transporting 
diseased plant material. Animals, insects, 
splashing rain, flowing water, and wind- 
blown dust are also common disseminat- 
ing agents. 

Several hundred types of bacteria cause 
plant disease. The most common types of 
disease caused by bacteria are soft rots, 
leaf spots or blotches, blights, stem rots 
or cankers, wilts, and galls. 

Bacteria, the simplest of plants, over- 
winter (or oversummer) on or inside 
perennial or winter annual plants, seeds, 
plant refuse, garden tools, or in soil. A 
few may even live for several months or 
longer in the bodies of living insects. 

Fortunately most disease-causing bac- 
teria are quickly killed by high tempera- 
tures, dry conditions and strong sunlight. 
Many bacteria in the soil, capable of 
causing plant disease, are inhibited by 
antibiotic substances secreted by other 
soil-inhabiting organisms (chiefly bacteria 
and fungi) . 

Fungi. Fungi, like bacteria, are also 
simple plants which lack chlorophyll. 
They obtain their food from living plants 
and animals or from decaying, nonliving, 
organic material. Together with bacteria, 



fungi break down organic matter into 
nutrients which can be utilized by garden 
plants. If it were not for fungi and bac- 
teria, our world would probably be piled 
many feet deep with dead plant and 
animal remains. 

The top foot of soil in 1,000 square 
feet of garden contains about 30 pounds 
of fungi. 

A typical fungus usually starts life as 
a microscopic spore which can be com- 
pared to the seed of a higher plant. Un- 
der moist conditions the spore may ger- 
minate and produce one or more 
branched threads called hyphae. The 
hyphae grow and divide to form fungus 
bodies called mycelia. Hyphae may pene- 
trate a plant by growing into a wound, 
through a natural opening, or by forcing 
their way directly through a plant's pro- 
tective "skin" or epidermis (see Figure 
3). 

The fungus body composed of an in- 
terwoven mass of hyphae usually gives 
rise to spores or spore-bearing bodies, 
completing the life cycle. The life cycle 
of certain fungi (e.g., rusts) are extreme- 
ly complex and may involve a number of 
different spore stages and more than one 
plant host. See (8) Rust, under General 
Diseases in the next section. 

Most fungi are rather inconspicuous 
but certain molds, mildews, and mush- 
rooms are known to almost everyone. 
Some have fruiting bodies which are two 
feet in diameter and weigh up to fifty 
pounds or more! Some of the large puff- 
balls contain billions of spores. 

Spores come in many different shapes, 
sizes, and colors (see Figure 3) . Perhaps 
"average" fungus spores when laid end to 
end would total 2,500 to an inch. 

Spores play an important part in the 
multiplication, dissemination, and sur- 
vival of fungi. Spores are easily carried 
by wind, water, insects, man, animals, 
plant parts (e.g., seeds, bulbs, etc.) , and 
equipment. 

Certain fungus spores have been 
known to blow a thousand miles or more, 
sometimes at high altitudes, before de- 
scending (frequently in a rainstorm) and 
infecting plants. 

Resting spores often allow the fungus 
to withstand unfavorable growing condi- 
tions such as extreme heat, cold, drying, 
and flooding. Spores of certain fungi may 
lie dormant for a number of years. When 



10 CAUSES OF DISEASES 




Fig. 3. Fungi. A. Various spore forms visible with a microscope, B. Different structures 
on which fungus spores are borne, C. Successive stages in germination of spores 
(1), followed by penetration into a leaf (2) through stomates, and establishment of in- 
fection (3). Fungus spores usually need a film of moisture on the surface of a leaf in 
order to germinate and penetrate plant tissue. 



they persist in the soil, they are very 
difficult to kill. 

Certain fungi do not produce spores. 
They multiply by forming compact 
masses of hyphae called sclerotia or by 
the fungus body dividing up into frag- 
ments which are broken off and spread 
by water, wind, man, and other agents. 

Bacteria and fungi are more prevalent 
and damaging to plants in damp areas 
or seasons than in dry ones. Moisture is 
usually essential to their rapid reproduc- 
tion, spread, penetration of plant parts, 
and infection of plant parts. 

Fungi cause the majority of infectious 
or parasitic plant diseases. They include 
all rusts, smuts, mildews, and scabs; many 
leaf spots, cankers, and blights; root, stem, 
and fruit rots; wilts; leaf galls; and others. 

Many parasitic fungi alternately live on 
dead and living plant tissues; others, like 
those causing the rusts and mildews, exist 
only on living plants. Fungi, like bac- 
teria, overwinter on and in plant refuse, 



soil, perennial plants, and seed or occa- 
sionally in insects. Most fungus spores 
and hyphae are easily killed by adverse 
conditions. Knowledge of these habits 
guides the development of effective con- 
trol measures. 

Viruses. Viruses are complex protein 
molecules which infect, multiply, mutate, 
and otherwise act like living organisms 
when in living plant or animal tissue. 
They are much smaller than bacteria 
(perhaps 250,000 or more to an inch) and 
cannot be seen with the ordinary lab- 
oratory microscope. 

A number of viruses have been crystal- 
lized in the laboratory. Yet they multiply 
only in the presence of living cells at the 
expense of normal proteins required by 
the plant. Hence viruses usually lead to 
abnormal growth expressed in various 
ways. 

The most common types of virus-caused 
diseases are mosaics, yellows, curly-top, 
spotted wilt, ringspots, stunt, and phloem 



CAUSES OF DISEASES 



11 



necrosis of elm. Many crop plants and 
weeds may harbor viruses but show no 
external symptoms, especially in hot 
weather. Certain variegated plants (e.g., 
Abutilon, Rembrandt tulips) are in- 
herently virus-infected. 

Viruses express symptoms which are 
often greatly variable even on different 
varieties of the same plant (e.g., stone 
fruits) . Viruses are consequently often 
grouped together generally by symptoms, 
regardless of true virus relationships. 
Symptoms of virus diseases pertain only 
to viruses with visible symptoms. 

Some plant viruses are quite infectious, 
being spread easily from diseased to 
healthy plants by mere contact. Others 
are transmitted in nature only by the 
feeding and plant-to-plant movement of 
insects (primarily aphids, leafhoppers, 
and thrips) . Practically all can be spread 
by propagating (e.g., grafting, budding, 
cuttings) virus-infected planting stock, 
and a very few by infected seed, pollen, 
soil, mites, nematodes, or possibly other 
minute animal life in the soil. 

Viruses often overwinter in perennial 
crops and weeds, in the bodies of insects, 
and in plant debris. 

Virus-caused diseases are receiving more 
attention by research workers now than 
formerly. This is partly due to a better 
understanding of viruses and to an ap- 
parent increase in the number of new, 
virus-caused diseases. How new viruses 
originate is not fully known. 

Nematodes. Nematodes that attack 
plants are slender, microscopic round- 
worms (often called nemas or eelworms) . 
The majority cannot be seen with the 
naked eye, rarely exceeding 1/20 of an 
inch long (see Figure 4) . Nematodes are 
common in water, decaying organic mat- 
ter, all moist garden soils, and tissues of 
other living organisms. Most types are 
harmless, feeding upon decomposing or- 
ganic material and other soil organisms. 
A few are even beneficial to man since 
they are parasitic on plant-feeding types 
or other pests. 

In order to grow and reproduce, para- 
sitic nematodes usually require living 
plants from which they suck plant juices, 
reduce vigor and afford easy entrance for 
wilt- or rot-producing fungi and bacteria. 
Nematode-damaged plants may also be 
more susceptible to winter injury. 

Nematodes may live part of the time 



(sometimes in the winter) free in soil 
around roots or in fallow fields and 
gardens. Parasitic nemas tunnel inside 
plant tissues or feed externally from the 
plant surface, especially the roots (Fig- 
ure 4) . Nemas may enter plants through 
wounds, natural openings, or by pene- 
trating the delicate roots and pushing in 
between the cells. 

Nematodes usually reproduce by laying 
eggs. These hatch, sometimes after months 
or even years, releasing young, wormlike 




Fig. 4. Nematodes. A. Nematodes feeding 
on surface of roots, B. Nematodes feeding 
inside a root, C. Nematode greatly en- 
larged showing internal structure. 

nematodes (larvae) which are usually 
born ready to start feeding. Nematodes 
multiply much faster than higher animals, 
but much more slowly than bacteria and 
fungi. 

Most parasitic species require three 
weeks or longer to complete a generation 
from egg through several larval stages to 
adult and back to egg again. Some nema- 
todes have only one generation a year. 
But the offspring in this one generation 
may number many hundreds. 

After a plant parasitic nema has been 
accidentally introduced into fields or 
gardens, it usually requires several years 
or longer before sufficient numbers (many 
millions of active nematodes per acre) are 
present to cause conspicuous disease 
symptoms in a large number of plants. 
This is because nematodes move very 
slowly through the soil under their own 
power — rarely more than thirty inches a 
year. 

Nematodes, however, are easily spread 
about by any agency involving moist, in- 
fested soil or plant parts. These include 



12 



CAUSES OF DISEASES 



all types of garden equipment and 
machinery, running water, shoes, feet of 
animals, and movement of infested plant- 
ing stock especially with soil around the 
roots. 

Only a few garden-infesting species 
cause typical plant disease symptoms. 
These include the root-knot nematode, 
leaf, bud, stem, and bulb nematodes, and 
possibly a few others. See Figures 36, 50, 
and 51. 

The best known nematode, the root- 
knot nematode, causes galls on plant 
roots. It is known to attack over 2,000 
kinds of plants. Most root-feeding species, 
however, cause no specific symptoms. In- 
fested plants often look as if they were 
suffering from drought, excessive soil 
moisture, malnutrition, or a disease (e.g., 
wilt, dieback, crown rot, or root rot) . 

Many times the first indication of nema- 
tode injury in a garden or field is the 
appearance of circular or irregular areas 
of stunted, sickly plants. These spots are 
small in the beginning and gradually en- 
large. Plants in the center may gradually 
die. The roots are often stunted, stubby, 
and discolored. 

It has been conservatively estimated by 
USDA nematologists that nemas get at 



least one-tenth of everything the farmer 
grows! Much of this loss could be avoided. 

It is necessary to examine the roots of 
unthrifty or abnormal plants, and also 
the surrounding soil for known parasitic 
types. This can be done only by a trained 
nematologist working in a well-equipped 
laboratory. If you suspect nematode in- 
jury, contact your local county extension 
office for information regarding collection 
of samples for identification of parasitic 
types. 

Certain nematodes live strictly in light, 
sandy soils. Some build up high popula- 
tions in muck soils; others seem to thrive 
best in heavy soils. 

Many species of nemas are easily killed 
by air-drying the soil while other types 
remain alive but in a dormant state. 
When dormant they are much more diffi- 
cult to kill by chemicals (nematocides; 
see Table 14 in the Appendix) or heat 
than when they are moist and actively 
wiggling. Crop rotation is often an im- 
portant control measure. Because com- 
plete control is impossible or unlikely, 
periodic checks are most desirable when- 
ever troublesome types have been found 
in large numbers. 



SECTION 2 



"What Is It?" 



ENVIRONMENTAL FACTORS 14 

1. Planting 14 

2. Soil 15 

3. Adding Organic Matter . 16 

4. Loosening Hard Soil . . 16 

5. Loose Soil Surface ... 16 

6. Soil pH 16 

7. Soil Test 17 

8. Nutrient Deficiencies . . 17 

9. Fertilizing Plants ... 18 
10. Pruning 20 

A. Shrubs 21 

B. Trees 21 

1 1. Tree Removal 22 

12. Treatment of Wounds . . 22 

13. Staking Trees and Shrubs 25 

14. Soil Drainage 25 

15. Watering 27 

16. Light 27 

17. Oedema 28 

18. Air Humidity 28 

19. Temperature 28 

20. Scorch or Sunscorch . . 28 

21. Winter Injury 28 

22. Chemical Injuries ... 29 

23. Mechanical Injuries . . 30 
Construction Damage . . 30 
Changing the Soil Grade 30 

24. Electrical Injuries ... 32 

25. Check and Double Check 32 

26. Here We Go 32 

GENERAL DISEASES 33 

A. Foliage Diseases .... 33 

(1) Fungus Leaf Spot . . 33 

(2) Bacterial Leaf Spot or 
Blight, Bud Rot . . . 33 

(3) Leaf Blight, Leaf Blotch, 
Anthracnose, Needle 
Blight, or Cast of Ever- 
greens 35 



(4) Shot-hole 37 

(5) Botrytis Blight, Gray- 
mold Blight, Bud Rot, 
Blossom Blight, Twig 
Blight 37 

(6) Downy Mildew ... 39 

(7) Powdery Mildew ... 41 

(8) Rust — Leaf, Stem, 

Needle 43 

(9) White-Rust, White 

Blister 47 

(10) Leaf Curl or Gall, Leaf 
Blister, Witches'-broom, 
Plum Pockets .... 47 

(11) Smut— Leaf, Stem, An- 
ther, and Seed ... 47 

(12) Sooty Mold or Blotch, 
Black Mildew .... 48 

(13) White Smut, Leaf Smut 50 

(14) Scab 50 

(15) Wilts 50 

A. Fusarium Wilt or 
Yellows .... 51 

B. Verticillium Wilt . 53 

C. Bacterial Wilt, 

Brown Rot, or 

Blight 55 

(16) Mosaic, Mottle, Crinkle, 
Streak, Calico, Virus 
Leaf Curl, Infectious 
Variegation, Flower 
Breaking 55 

(17) Spotted Wilt, Ringspot 57 

(18) Yellows, Aster Yellows, 
Rosette, Dwarf, Stunt . 58 

(19) Curly-Top, Western Yel- 
low Blight 60 

(20) Leaf, Bud, Stem, and 
Leaf Gall Nematodes . 60 



[13] 



14 



ENVIRONMENTAL FACTORS 



B. Stem Diseases 62 

(21) Crown, Foot, Stem, 
Stalk, Collar, or Rhi- 
zome Rot; Stem Blight, 
Southern Blight, Damp- 
ing-off 62 

(22) Stem, Twig, Branch, or 
Trunk Canker; Dieback; 
Stem, Cane, or Limb 
Blight 63 

(23) Wood, Butt, Wound, 
Heart, or Sapwood Rot 64 

(24) Fire Blight, Bacterial 
Shoot Blight, Bacterial 
Canker, Gummosis . . 66 

(25) Black Knot 66 

(26) Rust 66 

(27) Smut 66 

(28) Leafy Gall, Fasciation, 
Witches'-broom ... 66 

(29) Bacterial Soft Rot, Bac- 
terial Stem Rot, Collar 

Rot 67 

(30) Crown Gall, Cane Gall, 
Hairy Root, Bacterial 
Root Gall 68 



C. Flower and Fruit Diseases 70 

(31) Flower or Blossom 
Blight, Ray or Inflores- 
cence Blight 70 

(32) Fruit Spot, Speck, Rot, 
or Blotch; Seed, Berry, 
or Tuber Rot; Storage 

Rot 70 

(33) Smut 73 

D. Root and Bulb (Corm) 
Diseases 73 

(34) Root Rot, "Decline," 
Cutting Rot 73 

(35) Clubroot 73 

(36) Bulb (Corm) or Rhizome 

Rot 75 

(37) Root-knot, Root Gall, 
Cyst Nematode ... 75 

(38) Bulb Nematode, Ring 
Disease, Onion Bloat . 77 

E. Parasitic Flowering Plants 78 

(39) Mistletoes 78 

(40) Dodder, Strangle Weed, 
Love Vine, Gold Thread 80 



Accurate disease diagnosis is essential 
to curing the plant. It is much like 
detective work, for first you must find out 
all the facts and then put the facts to- 
gether like pieces in a jigsaw puzzle to 
make your case and reach a logical decis- 
ion. 

Let's take the sad case of Brother Juni- 
per's wilting aster plants. Is it because a 
wilt-producing fungus or bacterium has 
invaded the water-conducting tissues? Is it 
a root rot? Has a stem canker or rot shut 
off the supply of water to the foliage? 
How about the possibility of borers or 
root-feeding insects? Is the soil too dry, 
too compact and hard? Is soil drainage 
poor? Any one of these factors could 
cause the wilting. But which one? By care- 
ful observation of the plants, close 
checking of each factor, and with exper- 
ience, you have an excellent chance of 
reaching the right conclusion. 

Before discussing the general types of 
infectious diseases, let's briefly review 
some of the problems common to the 
culture of garden plants. These may 
either cause nonparasitic ailments or lead 
to infection by microorganisms. 

A complete discussion on the proper 
culture of plants would in itself constitute 
a volume of this size. In view of this, the 
discussion will be limited to difficulties 



which result from improper culture and 
which resemble plant diseases. For a good 
discussion on the culture of garden plants 
read a book such as The Care and Feed- 
ing of Garden Plants published by the 
American Society for Horticultural 
Science and National Plant Food Insti- 
tute, Washington, D.C. 

ENVIRONMENTAL FACTORS 
1. Planting 

Plants may wither and die or become 
sickly (leaves change color, often drop 
early) because planting instructions were 
not followed. Death usually occurs dur- 
ing the first year. 

Never allow the roots of plants to dry. 
On digging or receiving plants from a 
nursery, give the roots a good soaking 
and keep them damp until ready for 
planting. Keep them out of wind and 
away from heat. Whenever possible, pre- 
pare the planting holes in advance. 

For balled and burlapped evergreens, 
dig the hole about a foot wider and 
deeper than the ball. Be sure to handle 
by the soil ball only, since handling the 
plants may cause the ball to break or 
roots to pull loose from the ball of soil. 
Set the evergreen at the same depth it 
was in the nursery. If the soil is poor, ex- 



ENVIRONMENTAL FACTORS 



15 




Brother Juniper 



"Funny, you 

don't look a 

bit like your 

pictures!" 

(Courtesy 
Publishers 
Syndicate) 




Skx$-%~ 



cavate and prepare a good soil mix com- 
posed of rich topsoil, sand, and peatmoss 
or compost. Fill the hole 2/ s full, water 
thoroughly, cut the twine and peel back 
the burlap. Fill and pack firmly. 

For bare-root plants, dig the hole large 
enough to prevent crowding and twisting 
of roots. Loosen the subsoil. Put a 4-inch 
mound of topsoil in the bottom of the 
hole and spread roots in a natural posi- 
tion over it. Sever the roots which are 
broken and bruised. Set the plant at the 
same depth it grew in the nursery row. 
Work a crumbly, rich topsoil mixture, 
composed of i/ s peatmoss or compost, 
among the roots by hand as the hole is 
filled with soil. Fill the hole gradually. 
Soak the hole thoroughly when about 
1/4 full. Then settle the plant firmly by 
shaking gently. This assures contact of 
roots with soil and prevents air pockets. 
Pack the soil firmly. Leave a rim of soil 
at the edge to form a water-holding basin. 



Water deeply once a week (if less than 
1/4 inch of rain has fallen per week during 
the growing season) for the first two 
years. 

Shrubs next to the home should be 
planted at a distance of a little less than 
one-half the spread of a mature shrub. 
Don't crowd plants. Plant shrubs outside 
the eave line or overhang on a ranch-style 
home, especially on the north and east 
sides of the building. 

When soil is poor around the foun- 
dation, the entire bed should be dug 
out to a depth of \i/ 2 to 2 feet and re- 
placed with good soil. 

2. Soil 

Soil is probably the most important 
factor in the success or failure of grow- 
ing adapted or hardy plants. Healthy 
plants need a vigorous root system, ample 
soil nutrients (more correctly called ele- 
ments or raw materials) and a porous 



16 



ENVIRONMENTAL FACTORS 



soil containing the proper mixture of 
clay, sand, silt and humus or organic 
matter. Any soil can be improved! 

A good soil mixture for most house 
plants is made up of about 1 part each 
of good garden loam soil, organic matter 
(leafmold, well-rotted manure or compost, 
peatmoss), and coarse sand. Ferns, gar- 
denias and azaleas require soils with 
a higher content of organic matter, while 
cacti and many other succulents do best 
in a very sandy soil low in organic matter. 
Other special soil mixtures may be desir- 
able for certain plants, but they are the 
exceptions. 

3. Adding Organic Matter 

The addition of more organic matter 
will aid most garden soils. Mix in well- 
decomposed compost, peatmoss, or fresh 
barnyard manure. A compost pile (com- 
posed of layers of vegetable matter, 
animal manure, topsoil, and commerical 
fertilizer) in a back corner of the yard 
is an excellent investment. Check with 
your extension horticulturist on how to 
prepare a compost pile. If you have the 
land available, a green manure crop 
(e.g., ryegrass, soybeans, cowpeas, crim- 
son clover, a cereal, buckwheat, or Sudan 
grass) sowed in the spring and plowed 
under in late summer makes excellent 
organic matter. In all but the most north- 
ern states you can sow rye or winter 
wheat in late summer and plow it under 
in the spring. Fertilization before plow- 
ing under hastens decomposition of the 
green manure. This is often desirable. 
Sandy or heavy clay soils are especially 
benefited by adding organic matter. 

4. Loosening Hard Soil 

Hard, compact soil can be loosened by 
incorporating compost, wood shavings, 
weed-free straw, peatmoss, buckwheat or 
cottonseed hulls, grass clippings, leaves, 
chopped corn fodder and fresh manure 
with straw bedding. When the added ma- 
terial is low in nitrogen (e.g., wood shav- 
ings and straw), apply a nitrogen-contain- 
ing fertilizer to prevent crop injury. 

5. Loose Soil Surface 

Plants do best with a loose soil surface. 
This can be supplied by cultivation or, 
better still, by a surface mulch of organic 
material (see above) . The condition of 
your soil will be improved by mixing 
organic matter with it. 



6. SoilpH 

Is your soil acid or alkaline? This can 
be easily tested with an inexpensive soil 
test kit. Or you can take a composite soil 
sample and have it tested at your county 
extension office. The proper test will show 
the soil to be alkaline, neutral, slightly 
acid, or acid. Perhaps your test will be re- 
turned showing numbers on a pH scale. 
A pH of 7 is considered neutral. A pH of 
6 to 6.5 is slightly acid, and a pH of 4.5 
to 5.5 indicates the soil is acid or sour. Be- 
low pH 4 and above 9 most plants have a 
hard time growing. Soils in the United 
States range in pH from about 3.6 for 
certain acid peat soils to 9.5 for some 
black alkali soils. The favorable pH range 
for most crop and garden plants is 6.2 to 
7.5. 

The great bulk of garden plants are 
not particular as to soil reaction (pH) 
and will grow under a wide range of con- 
ditions. Exceptions are blueberry, dew- 
berry, huckleberry, hydrangea, andro- 
meda, camellia, some ferns, orchids and 
lilies, azalea, mountain-laurel, rhododen- 
dron, holly, white cedar, fir, fuchsia, gar- 
denia, gloxinia, heath, hemlock, ixora, 
juniper, larch, leucothoe, lily-of-the-valley, 
crapemyrtle, arbutus, scotch broom, mag- 
nolia, pine, spruce, tamarack, weeping 
willow, yew and a few others. The foliage 
of these plants may turn yellow (chlorotic 
or chlorosis) because of a lack of available 
iron or other elements which may be due 
to excessive lime. These plants are best 
grown in an acid soil with a pH of 4.2 
to 5.5 or 6.0. Soil can be acidified by add- 
ing aluminum sulfate, equal parts of 
powdered sulfur and iron sulfate, pine 
needles, or acid peatmoss (e.g., German 
peat or Michigan reed peat) to the soil. 
Aluminum sulfate, if overdosed, is toxic 
to plants. Use it with caution. The addi- 
tion of ^4 pound of sulfur per 100 square 
feet of garden increases the acidity of 
average soil about one pH point. Check 
with your extension horticulturist, county 
agent or nurseryman regarding acidifying 
soil. Replacing the soil about the roots 
with an acid soil may be preferable to 
acidifying the old soil. 

Liming is necessary in some areas to 
make the soil less acid. Avoid overliming. 
Too much lime can be as harmful to 
plant growth as too little lime. A good 
rule to follow is "lime by test — not by 
guess." Lime, when needed, is spread on 



ENVIRONMENTAL FACTORS 



17 



the soil and then worked into the top 6 
inches or so of topsoil. Finely ground 
dolomite limestone containing calcium 
and magnesium is the preferred form of 
lime in areas needing magnesium. Hy- 
drated lime, finely ground oyster shells, 
and marl may also be used. 

In the alkaline soils of large areas of 
the Midwest and arid parts of the United 
States many types of plants suffer from 
"iron chlorosis" unless the soil is acidified 
or iron-containing salts are placed in the 
soil root zone, injected into plants, or 
sprayed on the foliage. Chlorosis may also 
be caused by a deficiency of calcium, zinc, 
manganese, sulfur, viruses, and other para- 
sites. Excessive applications of lime may 
also induce iron, manganese, and zinc de- 
ficiencies. 

7. Soil Test 

If you suspect soil or fertilizer problems, 
contact your county extension office for 
advice. Frequently a soil test will be sug- 
gested to determine what, if any, fertili- 
zers or other treatments are advisable. 
County agents and their assistants know 
the soils in your area and what types of 
soil problems are most likely to occur. 
Only by a soil test can you be reasonably 
sure of what nutrients or other special 
care your soil needs. You can often save 
money by testing soil, since one or more 
nutrients may not be needed. Plants, like 
humans, differ in their individual nutrient 
needs. Plants in different stages of matur- 
ity also vary greatly in their tolerance to 
soil problems. Because soil tests are not 
infallible, certain plants may often re- 
spond to fertilization although the un- 
fertilized soil has sufficient nutrients for 
"less particular" plants. Different varieties 
of the same plant may even react differ- 
ently in the same soil! 

Special forms and mailing tubes are 
available at your county extension office 
for you to have your soil tested, usually 
for a nominal fee. 

8. Nutrient Deficiencies 

Plants growing in unfertile soil often 
appear sickly and weak. Abnormal foliage 
color may be due to a deficiency of one or 
more soil nutrients. Although more than 
50 elements are used by plants, only the 
more important nutrient deficiencies are 
discussed in this book. For additional in- 
formation, contact your extension horti- 
culturist or plant pathologist. Good, well- 



illustrated books on the subject include 
Hunger Signs in Crops, published by the 
American Society of Agronomy and the 
National Fertilizer Association and The 
Care and Feeding of Garden Plants, pub- 
lished by the American Society for Horti- 
cultural Science and the National Plant 
Food Institute. 

Stunted plants with small, pale green 
leaves, fading to yellow, often indicate 
a nitrogen deficiency. Plants are often 
spindly and weak. Nitrogen deficiency is 
probably the most common "hunger" sign 
in plants. Correct by applying a nitrogen- 
containing fertilizer, use legumes in the 
rotation, grow green-manure crops, or 
spray with nitrogen materials. Check with 
your county agent or extension horticul- 
turist. 

A superabundance of nitrogen may 
cause stunting, chlorosis, lack of fruit and 
flower development, and bud drop of rose, 
sweetpea, tomato, and other plants. 

Phosphorus-deficient plants usually 
have dark green leaves, followed by bronz- 
ing, reddening, or purpling, especially 
along the veins. Later, the leaves may de- 
velop purplish blotches. Plants and fruit 
are often stunted, mature late, and have 
shrunken seeds. Control by applying a 
complete commercial fertilizer or add 
separately as superphosphate. 

Potassium deficiency often is evident as 
a curling, scorching, browning, or bronz- 
ing of the leaf margins and tip. Older 
leaves are usually the first affected. Stems 
are weak and roots are underdeveloped. 
Plants are often stunted and appear 
"rusty." Correct by applying a complete 
fertilizer containing about 5 to 10 per 
cent potash. 

Iron, manganese, and zinc deficiencies 
frequently cause yellowing of the tissues 
between the veins on the youngest leaves 
(chlorosis) . See Figure 79. Later the en- 
tire leaf may become yellow, then cream- 
colored to white, and finally brown or 
scorched. Plants are often stunted. If 
severe, the foliage and growing tips may 
die. Control is by acidifying the soil, 
applying foliage sprays containing the 
sulfate form of iron, zinc, or manganese, 
or by the use of chelates of iron, man- 
ganese, or zinc as sprays, trunk injections 
or as ground applications. See under the 
plant involved. 

A lack of boron often causes plants to 
be stunted and brittle with a scorching of 



18 



ENVIRONMENTAL FACTORS 



the tips and margins of younger leaves. 
Older leaves are malformed and distorted 
while edible shoots, roots, and fruits are 
corky and discolored. Twig tips may die 
back. Symptoms are most severe in dry 
areas or seasons and in alkaline soils. In 
some areas boron is excessive, and crop 
injury to boron toxicity is not uncommon. 
Excess boron may cause plants to be 
stunted and yellowed or die prematurely. 
Germination may be delayed or prevented 
altogether. For additional information, 
read the USDA Information Bulletin No. 
211, Boron Injury to Plants. 

Magnesium deficiency symptoms usually 
appear on the older and lower leaves as 
a gradual fading of the normal green 
color at the margins, tips, and between 
the veins. Later these areas turn yellow 
(pink or red on some plants) and finally 
brown. When severe, the lower leaves die 
and may drop prematurely. The yellowing 
of the leaves progresses upward until only 
the tip leaves appear normal. In corn, or 
other plants with parallel veins, the 
yellowing appears as stripes. Control by 
using dolomitic limestone, magnesium- 
containing fertilizers or Epsom salts 
(magnesium sulfate) . 

Molybdenum deficiency causes Whiptail 
of cauliflower and broccoli (see under 
cabbage) . The leaves on other thin-leaved 
plants may be stunted, curled upward, 
pale or yellow in color, and malformed. 
The margins of older leaves die (red in 
beets) with symptoms progressing upward 
to the younger leaves. Plants vary greatly 
in their requirement for molybdenum. 

Plants also require copper in minute 
amounts. Lack of copper (principally in 
muck or peat soils of Florida and Cali- 
fornia) causes leaves to be darker green 
or even appear to have a bluish tint. Leaf 
edges curl upward and the green color 
gradually fades until it borders just the 
principal veins. Beginning with the low- 
est leaves, the pale areas in affected leaves 
gradually turn brown and die. Twigs may 
die back. Plants are stunted, and flower- 
ing is either delayed or checked alto- 
gether. Carrots are poorly colored and 
bitter. A deficiency of copper is easily 
checked by applying copper sprays to con- 
trol disease or by applying copper sulfate 
to the soil. 

A calcium deficiency causes the flower 
stem of gladiolus and tulip to topple. 
Roots of many plants are short and 



stubby. Twig tips may die back. Correct 
by spraying the growing plants with cal- 
cium nitrate or add ground limestone, 
dolomite or gypsum to the soil. 

Deficiency symptoms will not appear if 
the soil contains an ample, balanced sup- 
ply of available plant food, and the soil 
pH is favorable for growing plants. 

Starving plants, like starving animals or 
people, make poor growth and may be- 
come more susceptible to attack by cer- 
tain disease organisms. The causes of poor 
growth are often complex and frequently 
cannot be traced back to a lack of or ex- 
cess of some plant nutrient. Freezing tem- 
peratures, hot dry winds, drought, me- 
chanical injury, insects or diseases, pres- 
ence of nearby tree roots, too much sun 
or shade, poor soil drainage, etc., some- 
times produce effects that are comparable 
to nutrient deficiencies. 

9. Fertilizing Plants 

Use fertilizer carefully and as directed. 
Careful use can reduce maintenance and 
pruning requirements of shrubs. Don't 
overfeed. Excessive fertilizer applications 
may cause serious injury. Late summer ap- 
plications of fertilizer encourage tender 
growth in the fall which usually leads to 
severe winter injury. 

Growth is usually stimulated by an ap- 
plication of fertilizer, provided there is 
ample moisture in the soil. Well-main- 
tained and vigorous plants are also more 
resistant to disease and insect damage. 
The wounds of well-fertilized trees and 
shrubs also heal more quickly. 

Commercial fertilizers should always 
have a label which gives an analysis like 
10-10-10, 6-10-4, or 5-10-5. The first figure 
denotes the percentage of nitrogen (N) , 
the second, phosphorus (P) — actually 
phosphoric acid (P 2 O s ), and the third, po- 
tassium (K) — actually potash (K 2 Q) . 

The rate and methods of application of 
commercial fertilizers vary considerably 
with the individual needs of the plants in- 
volved and the purpose of the application. 

The time to fertilize garden plants de- 
pends on their characteristics. 

When preparing the lawn, vegetable, or 
flower seedbed, broadcast 1 to 4 pounds of 
a complete commercial fertilizer per 100 
square feet. More may be needed on light, 
easily leached soils. Work the fertilizer 
into the top 4 to 6 inches or more of soil. 

For established lawns spread the ferti- 



ENVIRONMENTAL FACTORS 



19 



lizer on the grass surface with a carefully 
calibrated lawn spreader and water it in 
immediately. 

For vegetables, flowers, small fruits, and 
other crops the fertilizer is frequently 
placed in a band or bands below or near 
the seeds or plants at the time of planting. 
The fertilizer is sometimes placed about 
2 inches from the seed in continuous 
bands 3 or 4 inches deep. 

Fertilizer is also often applied as a side 
dressing in a narrow furrow along or 
around these plants while they are grow- 
ing. Better check with your extension 
horticulturist on what and how much to 
use for your various plants. 

Leafy vegetables, such as broccoli, cab- 
bage, lettuce, and spinach do well when 
fertilizers fairly high in nitrogen are used. 
Root crops (beet, carrot, turnip, sweet- 
potato, white potato) respond to large 
quantities of both nitrogen and potas- 
sium. Beans, melons, and tomatoes require 
considerable quantities of nitrogen, phos- 
phorus and potassium. Many other ele- 
ments are needed as explained above. 

A starter solution of commercial ferti- 
lizer dissolved in water is used around 
many garden plants when they are trans- 
planted. The use of i/ 2 pint of starter so- 
lution for a vegetable or flower plant 
speeds up growth and often speeds up 
both maturity and yield. Set such plants 
as cabbage and tomato in place and fill 
the hole partly with water. The starter so- 
lution is then poured in and allowed to 
soak into the soil. Finally, fill the hole 
with dry soil. 

A multipurpose starter solution can be 
prepared by adding 2 or 3 ounces of a 5- 
10-5 or 6-10-4 fertilizer to a gallon of 
water. Stir until most of the fertilizer is 
dissolved or is in suspension. While using, 
stir to keep the plant food from settling 
out. If using a quick dissolving fertilizer 
which is concentrated, use one ounce per 
gallon or follow the manufacturer's di- 
rections. 

The foliar application of fertilizers in 
dilute concentration is particularly valu- 
able for applying trace elements (e.g., 
zinc, iron, manganese, boron, calcium, 
copper, etc.) . Many times these materials 
can be added to regular pest sprays. 

Avoid the use of "miracle" fertilizers 
that claim to contain mysterious plant 
foods and are sold at outrageous prices. 

Applications of fertilizer to trees and 



shrubs should be made in the spring or 
in late fall. For most purposes, use ferti- 
lizers with a 2-1-1, 1-1-1, or 1-2-1 ratio. A 
2-1-1 ratio would be approximated by a 
10-6-4 fertilizer. Examples of a 1-1-1 ratio 
are 10-10-10, 12-12-12, and 7-7-7. Examples 
of the 1-2-1 ratio include 10-20-10, 6-10-4, 
and 5-10-5. 

Fertilizer rates for trees are based on the 
diameter of the trunk at shoulder height. 
For young trees with trunk diameters 
from 2 to 6 inches (or large shrubs), use 
1 to 2 pounds of fertilizer for each inch 
of diameter. One pound of commercial 
fertilizer is enough if it contains 10 to 12 
per cent nitrogen. If the fertilizer contains 

5 or 6 per cent nitrogen, apply 2 pounds 
per inch of trunk diameter. 

Heavier rates are used for older trees 
with diameters over 6 inches at shoulder 
height. With fertilizers containing 10 to 
12 per cent nitrogen, use 1 to 3 pounds 
per inch. Apply 3 or 4 pounds per inch 
of trunk diameter if the fertilizer has 5 or 

6 per cent nitrogen. 

The fertilizer should be mixed with 2 
or 3 times its volume in topsoil and then 
packed into a series of holes 6 to 12 inches 
deep for young trees and 12 to 18 or even 
24 inches for larger trees. Bore the holes 
in the soil with a crowbar or soil auger. 
The hand auger drill is preferable since 
it does not compact the soil. Arborists use 
feeding needles and compressed-air drills. 
The holes are made about 2 feet apart in 
the ring and each ring is about 2 feet 
from the next one (Figure 5) . Proportion 
the total application of fertilizer-topsoil 
mixture between the holes as given above. 
Then wet the area thoroughly, using a 
lawn sprinkler or a fine spray from the 
garden hose. 

Less fertilizer is generally applied for 
evergreens than for deciduous trees. Fruit 
and nut trees should be fertilized regu- 
larly. 

Fertilize shrubs and most garden flow- 
ers by spreading the fertilizer in an area 
under the spread of the branches (Figure 
6) . The fertilizer should then be worked 
into the top several inches of soil and the 
area watered thoroughly. In most cases 
lawn fertilization is adequate for shrubs 
growing in the lawn. In borders and 
foundation plantings, apply fertilizer at 
the same rate as the lawn requires. 

House plants should be fed only when 
making active growth. From November 




Fig. 5. Fertilizing a tree by boring holes in the soil. Make the holes with a crowbar or 
soil auger. Punch holes 6 to 1 2 inches deep for young trees and 12 to 18 inches or 
deeper for large trees. The holes should be 2 feet apart and each ring about 2 feet from 
the next one. Place about 1 to 3 tablespoons of fertilizer in each hole — or enough to 
give the total application needed. Keep the rings at least 3 feet away from the trunk 
of young trees and at /east 6 feet on larger trees. The outermost ring should be beyond 
the drip line of the tree. 



through February they need very little, if 
any, additional feeding. Generally a com- 
plete fertilizer is recommended. A level 
teaspoon to a quart of soil before plant- 
ing is usually enough. After this apply the 
fertilizer in solution. Put a level table- 
spoon of a complete fertilizer in a quart 
of water. Let it stand overnight before 
applying. Water regularly to carry the 
nutrients to all the roots in the pot. Avoid 
overfertilizing! 

To avoid accumulation of excessive 
soluble salts in the root zone, periodically 
flush house plants with an amount of 
soft water equivalent to 5 or 6 times the 
soil volume. Check with your local flor- 
ist or extension horticulturist for addi- 



tional information regarding fertilizing 
of house plants. 

10. Pruning 

When bare-rooted trees and shrubs are 
transplanted, it is advisable to remove 
about 14 of the branch system. Even con- 
tainer-grown plants should be pruned. 
This reduces top growth and compensates 
for roots lost in moving. Broken, weaker, 
rubbing, diseased, and overcrowded 
branches should be removed whenever 
found. Do not cut back vigorous plants 
which have been thoroughly thinned out 
at the nursery. Follow instructions out- 
lined by your nurseryman. 

Prune just above a strong bud (Figure 



ENVIRONMENTAL FACTORS 



21 



7) . Each cut should be smooth. A smooth 
wound heals more rapidly. Prune to main- 
tain and improve the natural shape of 
each plant. Correct pruning restores vigor 
to older plants. 

Peaches and nectarines must be pruned 
every year. Cherries, especially the sour, 
require little special pruning. Apples and 
pears may not need much pruning for 
5 to 8 years after trees come into bearing. 
Later, of course, such trees should be 
pruned regularly. 

Judicious pruning results in more vig- 
orous plants, larger blooms, more fruit as 
well as control of the size and shape of 
the plant. 

A. Shrubs Prune sucker-type shrubs (e.g., 
spirea) by cutting about i/ s of the older 
mature stems to the ground (Figure 8) . 
Select a few of the better distributed stems 
(canes) to remain. Leave young vigorous 
growth. Cut suckers below the ground 
line and close to the parent stem. 

Prune shrubs which come up from a 
single main stem (e.g., honeysuckle) by 
removing some old branches at the base 
and others part way up. Leave young 
wood. But keep shrubs from becoming 
overgrown and straggly. 

Spring-flowering shrubs (e.g., forsythia, 
lilac, honeysuckle, spirea, and mock- 
orange) should be pruned right after 
flowering. Prune summer- and fall-flower- 
ing types (e.g., rose-of-Sharon, hydrangea, 
snowberry, and butterflybush) in the fall, 
winter, or early spring before flower buds 
form. Leave young wood but keep shrubs 
within bounds. 




If plants are grown partly for their at- 
tractive fruits (e.g., cotoneaster, pyra- 
cantha, and viburnum), delay pruning 
until the fruit fall. 

Prune clipped hedges frequently when 
young to insure heavy, compact growth. 
The top should be kept narrower than 
the base. This helps keep the base of the 
hedge compact as the bottom gets more 





Fig. 6. Fertilizing a shrub by spreading 
the fertilizer in a ring under the tips of 
the branches and beyond. The fertilizer is 
then worked into the top several inches 
of soil and watered in. 



A B C D 

Fig. 7. Pruning in relation to buds. A. 

Correct surface, B. Too much surface, C. 

Too long a stub, D. Too close to bud. 

light. Do not allow hedges to get taller 
and wider each year after they reach the 
desired size. Renovate old hedges by cut- 
ting the stems back to the ground. 
B. Trees Most trees can be pruned almost 
anytime during the year "when the knife 
is sharp" — except bleeders, i.e., maples. 
To promote quicker and better healing of 
wounds prune in the dormant season and 
in midsummer. 

Branches that are dead, dying, broken, 
or rubbing should be removed as soon as 
possible to improve the appearance and 
prevent entrance of disease-producing 
organisms and insects. Remove weaker, 
crowded, and rubbing branches while they 
are young. For fruit trees, remove all side 
branches except those desired to make 
permanent limbs. 

Follow the procedure outlined in Fig- 
ure 9 when removing limbs or branches. 
Cuts 1 and 2 are made to prevent strip- 
ping of the bark. Make each cut clean and 
flush with the stem or trunk. Don't leave 
short, useless stubs! These often lead to 
eventual wood root and premature death 
of the plant. 

Trees with narrow, V-shaped crotches 
(less than 45° angle) are subject to wind- 
splitting and later wood decay. One 
branch in the weak union is often re- 
moved while the tree is young. The nar- 
row crotch angles of certain trees (e.g., 



22 



ENVIRONMENTAL FACTORS 





Fig. 8. Pruning shrubs. A. Before, B. After. Prune 1o maintain and improve the natural 
beautiful shape of each plant. Remove old, dead, diseased, damaged, and interfering 

branches. 



elms) cannot be corrected in this manner. 
Here pruning back to the lower branches 
to reduce their weight, plus cabling and 
bracing is often necessary. 

The lower branches of shade trees grow- 
ing in lawns or along streets and side- 
walks should be removed while they are 
still small enough to cut off with hand 
shears. Continue each year until the low- 
est branch is the height you want it from 
the ground when the tree is mature (usu- 
ally 8 to 12 feet) . 

Narrow-leaved evergreens (e.g., yew, 
juniper, and arborvitae) may need an oc- 
casional light shearing to thicken the 
plants and keep them within bounds. 
Shear in late spring or early summer. 

Prune pines frequently to keep them 
compact. Do this in late spring when the 
new candle growth is full-grown but still 
soft. Firs and spruces require little prun- 
ing. Do it from late summer to winter. A 
little pruning of evergreens every year or 
two prevents a drastic operation at any 
one time. 

For additional help with your pruning 
problems contact your county agent or 
extension horticulturist. Many states have 
excellent pamphlets on this subject. The 
services of an experienced, responsible 
tree specialist should be employed for 
major pruning and for all hazardous aer- 
ial work. 



11. Tree Removal 

All dead, hollow, seriously diseased and 
structurally weakened shade trees are 
potential hazards to life and property. 
Such trees should be removed. As this job 
is hazardous, except in simple cases, it is 
important to secure the services of a com- 
petent arborist. 

12. Treatment of Wounds 

Wounds are treated to (1) prevent dry- 
ing of the tissues, (2) avoid infection by 
rot-producing organisms and insects, and 
(3) promote faster healing. 

Bark wounds and pruning scars should 
be promptly treated. Pruning cuts less 
than about an inch in diameter are not 
normally treated. Vigorous, well-main- 
tained trees heal faster then sickly, under- 
nourished ones. 

To heal quickly and properly, large 
wounds should be shaped. All splintered 
or diseased wood and bark should be re- 
moved cleanly with a sharp-edged knife or 
chisel (Figure 10) . Avoid leaving pockets 
where water may collect. If the job looks 
too big, call in a trained arborist. The 
margins of large wounds should be 
painted with shellac to prevent drying 
out. After protecting the margins, and 
excavating the cavity, all exposed wood 
should be sterilized by swabbing with a 
household bleach (diluted 1 to 5 with 




Fig. 9. Pruning trees — the right way and the wrong way. A. Tree topping "butchery." 
This is not a recommended way to prune trees (Courtesy Ottumwa, Iowa, Courier). B-D. 
The correct way to remove a large branch. B. Cut no. 1. C. Cut no. 2 severs the main 
part of the branch. These preliminary cuts prevent stripping of the bark. D. Final cut, 
made flush with the trunk, removes the stub. The wound should be promptly painted 
with a tree wound dressing. 





Fig. 10. Treating a tree wound. A. The clotted line indicates proper shaping for an ir- 
regular trunk wound. All margins should be cut back to live, healthy bark tissues. B. 
The bark has been removed cleanly together with some of the discolored or rotted wood 
beneath. The margins of the cut should be painted now with orange shellac. C. The 
wound has been completely cleaned and is ready to be painted with a tree wound 
dressing. D. Some time later. The old wound has been painted and rolls of callus 
growth are closing over the cavity. 



ENVIRONMENTAL FACTORS 



25 



water) or a 1:1,000 solution of mercuric 
chloride. See page 85 for details on how 
to prepare this solution and precautions 
to follow. 

Finally, all wounds should be painted 
with a permanent-type tree wound dress- 
ing. 

(1) Asphaltum-base tree paints with gil- 
sonite varnish are widely used and are 
available from many horticultural supply 
houses, garden supply stores, and nurser- 
ies. They are also available in aerosol- 
type cans. Those containing turpentine or 
coal tar will injure growing tissues. Buy a 
type containing a disinfectant (e.g., 0.25 
per cent phenyl mercuric nitrate) . 

(2) Outside-type house paints are fairly 
satisfactory if properly mixed with raw 
linseed oil. Use only after first coating the 
wound with orange shellac. 

(3) Bordeaux paint makes a good tree 
wound dressing. Prepare by slowly stirring 
raw linseed oil into fresh, dry, commercial 
bordeaux powder until a thick, sticky 
paint is produced. If you object to the 
blue-green color of the bordeaux, add 
lampblack suspended in oil. The disad- 
vantages of bordeaux paint are that it 
hinders rapid healing during the first few 
years, and it has rather poor weathering 
qualities. 

(4) The newest, and probably the best, 
tree wound dressings contain a mixture of 
lanolin, rosin, and gum. Some also have 
a disinfectant added to these ingredients 

(see above) . You can prepare a good tree 
paint by melting and stirring together 10 
parts by weight of lanolin, 2 parts of 
rosin, and 2 parts of crude gum. 

Tree wound dressings are also avail- 
able in convenient aerosol bombs. 

Wound dressings should be checked 
periodically. Recoat once or twice a year 
when the surface cracks, peels, or blisters. 

For additional information on treating 
wounds and cavities, as well as many other 
types of tree injuries, secure a copy of 
USDA Farmers' Bulletin No. 1726, Treat- 
ment and Care of Tree Wounds and 
Farmers' Bulletin No. 1896, Care of Dam- 
aged Shade Trees. 

The United States Department of the 
Interior, National Park Service, Tree Pre- 
servation Bulletin No. 3, Tree Bracing, 
gives an excellent account of the proper 
ways to cable and brace trees. Some of the 
same information is also given in Farmers' 
Bulletin No. 1896. 



All USDA bulletins mentioned above, 
or elsewhere in this book, are available by 
writing to the Superintendent of Docu- 
ments, U. S. Government Printing Office, 
Washington 25, D.C. There is often a 
small handling charge (usually 5 to 25 
cents) . 

To get a complete listing of United 
States government bulletins currently 
available, call at your county extension 
office. 

13. Staking Trees and Shrubs 

Just after planting in windy locations, 
treelike shrubs and small evergreen trees 
should be guyed (Figure 11) or supported 
by means of a single, stout stake driven 
into the ground on the windward side 
about a foot from the trunk. Care should 
be exercised to prevent damage to the 
root system. Attach the tree to the stake 
with guy wire threaded through scrap 
garden hose or larger tubing. Burlap with 
sash cord or light rope works nearly as 
well. Stake street trees, up to 3 inches in 
diameter, with two stakes on opposite 
sides of the tree about 18 inches from the 
trunk. Street trees of 4- to 6-inch diameter 
should have 4 stakes in a box formation 
18 inches from the tree. 

Guy shade trees up to about 5 inches 
in diameter from three directions as 
shown in Figure 11. Guy wires are usually 
removed the second year after transplant- 
ing, except in windy areas. Permanent 
guys (one or double strands of 12-gauge 
wire) should be attached by eyebolts or 
lag hooks inserted into the trunk or 
branches; never wrapped around them. 

14. Soil Drainage 

Soil underlaid with an impervious layer 
of clay, hardpan, or rock which drains 
poorly, may kill sensitive plants (e.g., 
roses, most evergreens) . When water col- 
lects above this impervious layer, the soil 
becomes saturated (waterlogged) . Home 
owners usually assume that sloping land 
provides sufficient soil drainage. This is 
often a false assumption because the soil 
below the surface may be tight, resulting 
in poor drainage. Water remaining in the 
root area forces air out, causing the roots 
to die from suffocation. This condition 
may kill plants outright or cause stunted 
and yellowish growth with reduced yields 
of flowers and fruit. Unless tolerant plants 
are grown, such soils should be drained by 



26 



ENVIRONMENTAL FACTORS 




Fig. 11. Guying trees. A. All three guy wires should have the same tension. D. The 
best method of fastening wires to trees using lag hooks, eyebolts, or screw eyes. B and 
C. Less satisfactory methods. 



deep tillage (using a subsoiler or lister) . 
Installing gently sloping lines of agricul- 
tural drain tile every 20 to 25 feet at a 
depth of 2 or 3 feet usually provides a 
permanent cure for a waterlogged soil. 



Check with your county agent if you have 
soil drainage problems. 

If soil is permanently waterlogged or 
swampy (oxygen deficiency or asphyxi- 
ation) and cannot be drained, it may be 



ENVIRONMENTAL FACTORS 



27 



necessary to grow plants adapted to these 
conditions (e.g., bog plants) . 

Lack of vigor and off-colored foliage 
are two signs of poor soil drainage. Your 
soil should have good natural drainage to 
a depth of at least 2 feet, preferably 
deeper for trees. 

15. Watering 

Excessive moisture, droughts, or un- 
favorable temperatures cannot always be 
prevented, but their injurious effects can 
often be reduced. During hot, dry periods 
shrubs need extra water, especially when 
growing in a lawn. Plants lose water 
rapidly under such conditions and unless 
watered, severe wilting, withering, and 
death often result. Almost the same 
symptoms may follow excessive rainfall 
and overwatering. It is not true that 
plants are injured by watering on a hot, 
sunny day. 

Shrubs and trees planted in the spring 
usually die during hot summer weather 
if the soil is not kept sufficiently moist. 
During droughts, plants in unfavorable 
locations (light sandy soils, slopes, winds, 
or full sun) are the first to suffer. Leaves 
may wilt, become scorched, and drop 
prematurely. If many of the feeder roots 
are killed, the entire plant may die. In- 
jured trees and shrubs usually die slowly 
over a period of one or two or more years. 
Timely detection and treatment could 
save many valuable plants. 

Drying out of soil is often disastrous 
for pot plants, evergreens, newly planted 
trees, shrubs, transplants, and new lawns. 
Grass and garden plants growing beneath 
trees, or areas filled with tree and shrub 
roots are difficult to keep watered. 

Maximum growth from most plants in 
roughly the eastern half of the United 
States comes when they have an equiva- 
lent of an inch of water (from rainfall or 
irrigation) a week during the growing 
season. Much more water than this is 
needed in arid areas of the western states 
where moisture is greatly deficient. During 
droughts, water enough so that it soaks 
the soil to a depth of at least 8 to 12 
inches, preferably more for deeper-rooted 
plants. After the sprinkler has been on 
an hour or more in the same spot, use a 
trowel to check the depth of water pene- 
tration. 



House plants should be planted in 
light, well-drained soil and not over- 
watered. Nearly all of these plants require 
a steady supply of water with the ex- 
ception of cacti. A drainage hole should 
be present in the bottom of the growing 
container. Only experience will tell you 
how much water your house plants need. 
Lack of water causes wilting, leaf scorch, 
early dropping of leaves, root injury, and 
stunting among other troubles. 

Does your home have wide, overhang- 
ing eaves? Do you always remember to 
give the soil underneath extra water? If 
you live in a windy location or in a dry 
region, it is even more necessary that 
perennial plants, especially evergreens, 
have adequate moisture during late fall 
and winter. 

16. Light 

Plants vary greatly in their require- 
ments for light. Some thrive best in full 
sunlight; others need shade or partial 
shade to do their best. 

Extremely high 1 i g h t intensity, 
especially during hot weather, may cause 
sunscalding of fruits and vegetables or 
result in the fading of deep flower colors. 
Valuable plants may be at least partially 
protected by spraying the foliage with a 
material like Wilt-Pruf before scorching 
occurs. 

The duration of the light also affects 
flowering and fruiting. Short-day plants 
such as chrysanthemum, cosmos, tuberous- 
rooted begonia, and poinsettia bloom 
when the day length is 12 hours or 
shorter. Long-day plants such as corn and 
peas are stimulated to flower when the 
day length is 14 hours or longer. Other 
plants such as tomato are day-neutral and 
do not respond to short or long days. 

When planning your foundation and 
garden plantings, check on the light re- 
quirements for the various plants you 
plan to grow. This will save you both 
money and later grief. Shrubs for the 
north side of a home must be selected for 
shade tolerance. 

Most flowers, vegetables, and flowering 
shrubs (e.g., lilac, viburnum, spirea) 
require full sun for at least a part of the 
day. Such plants as laurel, rhododendron, 
and azalea will blossom in partial shade. 

Give most house plants as much light 



28 



ENVIRONMENTAL FACTORS 



as possible, especially during the winter 
months. Such plants should be placed by 
a window, except plants that do not thrive 
in strong sun (e.g., ferns, begonias, cycla- 
men, African-violet, and foliage plants) . 
To produce flowers, most house plants 
need 3 to 5 hours of direct sunlight a day. 
A lack of sufficient light often leads to 
pale green leaves, spindly growth, leaf 
drop, and loss of flowers. 

Artificial light may be supplied by 
fluorescent tubes to provide from 300 to 
600 foot candles at the top of the plants. 
Give most plants 12 to 18 hours per day 
of this supplementary light, if needed. 

17. Oedema 

A common problem with indoor plants. 
Small masses of leaf or stem tissue may 
expand and break out, causing watery 
swellings or galls. Later the exposed sur- 
face may become rusty in color and corky 
in texture. Control by reducing air hu- 
midity, increasing light and air circula- 
tion, plus avoiding overwatering es- 
pecially during overcast periods. Oedema 
is a nonparasitic disease. 

18. Air Humidity 

The low humidity in a city apartment 
or modern home is often responsible for 
the leaves of begonias, ferns, rubber plants 
(Ficus) , and others becoming spotted or 
scorched and falling prematurely. Plants 
taken from a cool, moist greenhouse or 
florist's shop to the hot (75° to 85° F.) dry 
air of a home are commonly affected. 
Many times the flowers suddenly drop off. 
Control by increasing the humidity 
around susceptible plants and reducing 
the temperature. Buy a ready-made hu- 
midifier or build one yourself. Set plants 
on an inverted pot over a large pan of 
water, in a glass or plastic case, or in a 
planter filled with sphagnum moss or 
other filler which is thoroughly wet down 
occasionally. Evaporation of a gallon of 
water a day for the average room should 
moisten the air enough for plants. Your 
florist can also provide tips on increasing 
the air humidity during dry periods such 
as winter. 

The average home is too dry for fungus 
or bacterial diseases to develop on the 
foliage of house plants. 



19. Temperature 

Most house plants do best if the day- 
time temperature is between 65° and 
75° F. and at night 55° to 60° F. Most 
modern homes are too warm for the best 
growth of many house plants. Since it is 
often not practical to keep the temper- 
ature within the limits outlined, there are 
two alternatives: (1) select plants that 
"get along" at higher temperatures, or (2) 
replace flowering house plants after 
several weeks when blossoming is com- 
plete. 

For top results, place your flowering 
plants in cool locations at night, away 
from radiators and heat registers. Avoid 
putting such sensitive plants as African- 
violet close to windows during cold, win- 
ter weather. 

Vegetables, too, are sensitive to temper- 
ature. Cauliflower and head lettuce grow 
best in cool weather. Celery, cabbage, and 
certain other vegetables may shoot up seed 
stalks if the temperature is 50° F. or below 
for a period of time when plants are 
young. Tomatoes and peppers often drop 
their blossoms during temperature ex- 
tremes when night temperatures range 
from 55° to 60° F. and day temperatures 
are about 95° F. or above. High temper- 
atures are also responsible for the pre- 
mature flowering of spinach, broccoli, and 
lettuce and the low yield of garden peas 
and beans. 

20. Scorch or Sunscorch 

During very hot (90° F. or above) , dry, 
windy weather the tips and margins of 
the leaves on many plants, especially trees, 
turn brown and wither (Figure IB) . In- 
jury occurs when water is lost by the 
leaves faster than it can be replaced by 
the roots. Scorching may progress inward 
until entire leaves turn brown and wither. 
Such symptoms may also be caused by 
other conditions or by a parasite. Sun- 
scorch can often be checked by watering 
plants during summer droughts, pruning 
to open up trees and shrubs, mulching 
plants, and shallow cultivating. 

21. Winter Injury 

Trees and shrubs growing in exposed, 
windy locations or in poorly drained soils 



ENVIRONMENTAL FACTORS 



29 



may be injured by low temperatures, 
alternate freezing and thawing, or drying 
winter winds. Plants overfed with a high- 
nitrogen fertilizer or those still actively 
growing in late fall are most commonly 
injured. Frost cracks, a vertical separation 
of the bark and wood, are common on 
many young, thin-barked trees on the 
south or southwest sides of the trunk. In- 
jury to broad- and narrow-leaved ever- 
greens occurs following extreme and rapid 
fluctuations in temperature or by early 
fall or late spring freezes. Plants growing 
in sunny areas are most subject to injury. 
Plants prone to winter injury and sun- 
scald may be grown where shaded from 
midday or late afternoon sun — or shade 
may be provided by a cheesecloth or lath 
screen. Protect trunks of young, thin- 
barked trees from winter sunscald and 




&.. 



Fig. 12. Three methods of protecting trees 
against winter injury. A. Wrapping with 
sisalkraft paper or burlap, B. Use of a 6- 
inch board on the south side, C. Wrapping 
young trees with aluminum foil. 

frost cracks by wrapping with burlap 
strips, sisalkraft paper, aluminum foil, or 
just tie a 6-inch board upright on the 
south side of the tree (Figure 12) . 

Protect exposed evergreens from leaf 
scorching, caused by drying winter winds 
and sun, by erecting canvas or burlap 
screens on the south and southwest sides. 
Better still, plant in a more protected 
location! Try covering the foliage with 
a special "no-wilt" (e.g., Wilt-Pruf or 



Plant Cote) spray in autumn. Evergreens 
should be watered during late fall and 
early winter. Then apply a 2-inch mulch 
of sawdust, shavings, peatmoss, or leaves. 
Mulching helps prevent deep freezing or 
alternate freezing and thawing after the 
ground is frozen, allowing more water ab- 
sorption by the roots. 

A sharp variation in soil and air tem- 
peratures may cause abnormal growth. 
Low winter temperatures and late spring 
or early fall freezes may cause injury 
similar to burning, especially if the plants 
have made late, tender growth. 

Check with your extension horticultur- 
ist or county agent on what, how, and 
when to apply winter protection to your 
garden plants. He can help you select 
plants which are adapted and will do well 
in your particular location. 

Additional help can be obtained by 
studying the USDA Miscellaneous Publi- 
cation No. 184, Plant Hardiness • Zone 
Map. Numerous indicator plants are listed 
for each of the 10 hardiness zones in the 
United States. 

22. Chemical Injuries 

Sometimes in and near large cities such 
as Los Angeles, smelters, factories, and 
incinerators create impurities in the air 
which result in leaf discoloration or poor 
growth. These impurities include ethyl- 
ene, fluorides, herbicides, oxidized hydro- 
carbons (smog) , ozone, and sulfur di- 
oxide. Plant responses to polluted air may 
depend on the plant variety, soil fertility 
and moisture, and the temperature. 

Ingredients in automobile exhaust 
fumes contain products which are harm- 
ful to plants. Smog damage in large cities 
can be prevented by spraying susceptible 
plants with Ozoban (Charles Pfizer & 
Co.) or other trade products containing 
ascorbic acid. Fungicide sprays containing 
zineb, maneb, ferbam, dichlone, or thiram 
often reduce damage. Sprays should be 
applied periodically during the smog sea- 
son. Check with your local nurseryman or 
extension horticulturist. 

Salt injury, whether it occurs along a 
seacoast where salt water sprays are blown 
inland or along sidewalks and driveways 
where salt is applied for weed control may 
cause scorching and killing of leaves sim- 
ilar to that caused by certain diseases. Salt 



30 



ENVIRONMENTAL FACTORS 



applied on country roads or driveways to 
keep down dust, or on city streets to 
speed the melting of snow and ice may 
damage tree roots when washed or swept 
down into the soil. 

Trees, shrubs, and other plants often 
show scorched leaves and wilt along 
streets or other places where manu- 
factured illuminating gas lines are buried. 
When these lines develop leaks, the gas 
penetrates and poisons the soil, killing 
nearby plant roots. Sudden or gradual 
severe wilting, dieback, or other peculiar 
symptoms, frequently occur depending on 
the size of the leak and the period of 
time illuminating gas has been escaping. 
If you suspect poisoning, call the gas 
company. Natural gas, which has largely 
replaced illuminating gas, supposedly does 
not contain the plant-toxic materials (e.g., 
unsaturated hydrocarbons, hydrogen 
cyanide and carbon monoxide) found in 
manufactured illuminating gas. 

Well-established plants sometimes are 
damaged by too much care (excess water 
or fertilizer or both) by overanxious home 
owners and careless workers. 

Careless use of weed killers may result 
in severe injury or even death of trees, 
shrubs, and annual plants. Weed-killing 
chemicals containing 2,4-D, 2,4,5-T, Ami- 
trol, or arsenicals should be used with ex- 
treme care. Follow the manufacturer's di- 
rections to the letter! 

The pesticides recommended in this 
book will not normally cause damage to 
plants if applied according to the manu- 
facturer's directions on the plants speci- 
fied, at the rates specified, and at the times 
specified. Injury is most apt to occur on 
tender growth or when plants are in a 
wilted condition. Bordeaux mixture and 
other copper-containing fungicides may 
cause a scorching and spotting of leaves 
on certain plants during cool, wet 
weather. Copper-injured plants may be 
stunted with blossoming and fruit-setting 
delayed. Sulfur, Karathane, Acti-dione, 
and the so-called dinitro materials may 
cause scorching in hot (above 85° F.) dry 
weather. Insecticides, including dormant 
oils, arsenicals, malathion, parathion, 
DDT, and nicotine sulfate may also dam- 
age certain types of plants. Precautions 
are usually listed on the package label. 

23. Mechanical Injuries 

Mechanical damage caused by lawn 
mowers, automobiles, hailstones, wind, ice 



and snow, and boys' knives often results 
in poor growth, weakened plants, and 
wood rot. Such injuries should be treated 
promptly (Figure 10) . 

Strangling tree roots which grow tightly 
around the trunk and other roots may 
weaken and kill trees. Such girdling 
roots, which may be above or below 
ground, should be cut off with a chisel 
and mallet and the exposed surface 
painted. You can help decrease the pos- 
sibility of girdling roots by spreading the 
roots out naturally when planting (see 
1 above) . Treating of girdling roots may 
also be a job for a good arborist. 

Digging a basement or foundation near 
large trees results in the cutting away of 
many valuable feeding roots. If the 
wounds are not promptly treated, wilt 
and root-rotting fungi may enter. The 
water table for the remaining roots may 
be changed. The effect may cause death of 
trees. 

Construction Damage Construction dam- 
age to shade trees is common by sloppy 
workmen building a new home. Tree 
roots are broken, cut, or exposed — or 
trunks are brutally scraped. Tractors and 
bulldozers compact the soil making condi- 
tions unfavorable for root development. 
Injury to tree roots also occurs when 
trenches for utility lines are dug or lawn 
grading occurs. 

Cuts and bruises permit easy entrance 
for rot-producing fungi which commonly 
attack weakened trees and shrubs. Be sure 
wooden or metal barriers are put up to 
protect valuable shade trees while con- 
struction is going on. 

Changing the Soil Grade Another common 
construction damage problem for new 
homes is a change in soil grade around 
trees. Roots are exposed when soil is re- 
moved or a heavy, compacted, clay soil 
fill smothers the root system. Even several 
inches of this type of fill can kill old, 
shallow-rooted trees. Trees suffering from 
too much fill soil will have smaller leaves 
than normal, and dying back of the outer 
and upper twigs and branches occurs. 
Sucker growth on the trunk is common. 
Fill-injured trees may take up to 10 years 
to die. 

Nothing can be done to save trees bur- 
ied under a fill for a long time, which 
have dead or dying tops. Recent fills, or 
trees which are apparently not suffering 
seriously from older fills can be treated. 




Fig. 13. Preventing injury when constructing a deep soil fill. A. Side view showing (1) 
the dry well; (2) ground tile, sloped to drain away from the trunk and off the roots; (3) 
vertical bell tile, connected with the drain; (4) metal grating to prevent falling into dry 
well. The tiles (2) and (3) are covered with rock and coarse gravel except for a foot of 
topsoil. B. Top view of A showing the trunk at the center surrounded by a dry well with 
6 lines of tile radiating out to the ends of the branches. The ground tiles are connected 
by a row of tiles around the outside. Upright bell tiles are at all intersections. C. Pro- 
tecting arch of stone is placed over drain tiles to prevent breakage. D. Vertical bell 
tile rest on the ends of horizontal ground tile that are spaced to allow for air circulation. 



32 



ENVIRONMENTAL FACTORS 





Fig. 14. Preserving a maximum of roots when lowering a soil grade. A. By terracing, 
B. By erecting a retaining wall. The original soil grades are shown by the dotted lines. 



Start corrective treatments at once. At- 
tempt to recreate, as much as possible, the 
prefill conditions. Where a fill is ao- 
solutely necessary, use a rock or brick well 
around the tree. Installing a wagon wheel 
design of tile drainage over the root area 
before making the fill is recommended for 
deeper fills (Figure 13) . No single method 
of constructing fills over tree roots fits all 
circumstances. An excellent USDA Farm- 
ers' Bulletin, No. 1967, Reducing Damage 
to Trees from Construction Damage, 
covers this subject in detail. Before mak- 
ing grade changes around large trees, call 
in an experienced landscape architect or 
arborist for his advice. 

24. Electrical Injuries 

Lightning damage is quite common, 
particularly on tall, isolated trees such as 
elm, maple, oak, pine, poplar, and tulip 
or yellow-poplar. Trees may suffer no 
permanent damage, show streaks of split 
bark and wood which extend to the 
ground line, or be completely shattered. 
If you suspect lightning damage, call in 
a competent arborist. Lightning-protec- 
tion equipment is available for trees. 

Wires carrying electric current through 
trees, or near trunks and branches, should 
be covered with nonconductors at critical 
points. Be sure that the lights used on 
outdoor Christmas trees are properly 
placed and equipment is not worn. You 
don't want to damage that prized ever- 
green. 



25. Check and Double Check 

Before blaming an infectious disease for 
an ailing plant, check the soil, water sup- 
ply, light requirements, winter protection, 
and other factors mentioned above. Have 
you carried out recommended cultural 
practices in planting, pruning, and ferti- 
lizing? Is an insect, mite, or rodent pest 
involved? How about spray or fume in- 
jury? If you eliminate all these, and the 
other possibilities outlined above — then 
one or more infectious diseases may be the 
answer. Find out exactly what is wrong 
and resolve to start control measures 
earlier next year. 

When investigating a plant trouble, 
examine the symptoms carefully. If you 
suspect an infectious disease, read the 
disease descriptions listed under the plant 
involved. Think back and consider what 
else might have gone wrong. But don't 
rush out and buy a new spray or dust "be- 
cause the old one didn't work." Remem- 
ber, by the time the blight, rot, or leaf 
spot is serious enough to be noticed, it's 
probably too late for spraying or dusting 
to do much good this season anyway. 

A leading plant doctor, Dr. Cynthia 
Westcott, once said, "The chief hazard 
any garden plant has to endure is its 
owner or gardener." She also says don't 
jump to conclusions when a plant be- 
comes sick. 

26. Here We Go 

Most plant diseases are named in ac- 
cordance with their most conspicuous 



GENERAL DISEASES 



33 



symptom or symptoms, just as many 
human and animal diseases are described. 

Diseases which, in general, look alike 
have often been lumped together even 
though they may be caused by different 
organisms. This is possible where control 
measures for each are the same. Where 
control measures are different, these have 
been pointed out under the plant in- 
volved. 

We have arbitrarily divided the differ- 
ent general types of diseases into those 
which principally attack the foliage, stems 
(including trunks, branches, and twigs) , 
roots, flowers and fruit. Many times the 
same organism attacks more than one 
plant part and hence may be listed in 
more than one category. 

Although the diseases listed are based 
on records in the continental United 
States, a majority of these diseases is 
found wherever these plants are grown 
in the world. 

GENERAL DISEASES 
A. Foliage Diseases 

(1) Fungus Leaf Spot Usually a rather defi- 
nite spot — of varying size, shape, and 
color depending on the cause. Often with 
a distinctive margin. Spots are often zon- 
ate or marked with conspicuous concen- 
tric zones. If they are numerous, or if 
they enlarge, diseased areas may join to- 
gether forming irregular blotches or a 
blight. Infected leaves may wither and 
die prematurely. See (3) Leaf Blight. 
Certain leaf spots have special names such 
as black spot, tar spot, spot anthracnose , 
or anthracnose. The centers of some spots 
may fall out leaving holes. See (4) Shot- 
hole. 

Leaf spots are the most common of all 
diseases. They are favored by wet seasons, 
high humidity, and water splashed on the 
foliage. 

Plants Attacked: Practically all plants. 
Control: Most leaf spots are not serious 
enough to warrant special measures. 
Where practical (or possible) , collect and 
burn infected plant parts when first evi- 
dent and at the end of the growing season. 
Rotate garden plants avoiding members 
of the same plant family in the same soil 
in successive years. Plant disease-free seed 
or treat as directed under the plant in 



question and in Table 13 in the Appen- 
dix. Control insects and mites (which 
may carry the causal fungus around) 
using malathion plus DDT or methoxy- 
chlor. Follow the suggested spray or dust 
program for the plant involved. Use cap- 
tan, zineb, maneb, ziram, or a copper-con- 
taining fungicide. See Section 3 for in- 
formation about these chemicals. 

Protection for trees and shrubs is usu- 
ally needed when leaves are expanding in 
the spring. Some plants such as roses r 
tomatoes, and apples may need regular 
applications through the growing season. 
Keep plants vigorous by fertilizing and 
watering. Grow resistant varieties when 
available. Indoors, keep water off the 
foliage and the humidity as low as prac- 
tical. Too low humidity probably causes 
more damage to house plants than organ- 
isms producing leaf spots and blights. In- 
crease air circulation by spacing plants, 
especially those in shaded areas, plus re- 
moving the lower 4 to 6 inches of foliage 
on certain plants (e.g., phlox, chrysanthe- 
mum, and roses) . 

(2) Bacterial Leaf Spot or Blight, Bud Rot 
Symptoms variable; dark, water-soaked 
spots or streaks often develop on leaves 
and stems which later turn gray, brown, 
reddish-brown, or black. Spots may even 
drop out leaving ragged holes. Leaves may 
wither and die early. On crucifers (cab- 
bage, cauliflower, and related plants) V- 
shaped, yellow, brown, or dark green 
areas develop in leaves with blackened 
veins. See also (15C) Bacterial Wilt, (24) 
Fire Blight, and (29) Bacterial Soft Rot. 
Plants Attacked: Aconitum, almond,, 
apple, apricot, arrowwood, artemisia, 
asparagus-bean, avocado, barberry, bean,, 
beet, begonia, belamcanda, blueberry,, 
boxelder, broccoli, Brussels sprouts, bry- 
onopsis, butternut, cabbage, California- 
laurel, California-poppy, canna, canta- 
loup, carnation, carrot, cassaba, castor- 
bean, catnip, cauliflower, celery, cherry, 
cherry-laurel, chicory, Chinese cabbage, 
Chinese hibiscus, Chinese lanternplant, 
chrysanthemum, collards, corn, cotton- 
rose, cucumber, cranesbill, currant, del- 
phinium, dieffenbachia, eggplant, endive, 
English ivy, escarole, European cranberry- 
bush, ferns, filbert, flowering almond, 
flowering cherry, forsythia, gardenia, 
geranium, gladiolus, gourds, grapefruit, 



* 




HEALTHY 
DISEASED ► 






HEALTHY 



DISEASED ► 




Fig. 15. Four leaf spots caused by fungi. A. Iris leaf spot, B. Septoria leaf spot of to- 
mato, C. Black spot of rose, D. Strawberry leaf spot. 



GENERAL DISEASES 



35 



groundcherry, hazelnut, heronsbill, hibis- 
cus, honeydew melon, horseradish, hy- 
acinth, hyacinth-bean, iris, Jerusalem-arti- 
choke, kale, kohlrabi, larkspur, lettuce, 
lilac, magnolia, maple, monkshood, mul- 
berry, muskmelon, mustard, narcissus, nas- 
turtium, nectarine, onion, orange, orchids, 
palms, pea, peach, pear, pepper, philo- 
dendron, plum, poinsettia, poppy, potato, 
primrose, privet, proboscisflower, scarlet 
runner bean, pumpkin, pyracantha, rad- 
ish, rape, rhubarb, rose, rose-of -Sharon, 
rutabaga, seakale, squash, stock, sunflower, 
sweetpea, tigerflower, tomato, tree-tomato, 
turnip, viburnum, walnut, watermelon, 
and West Indian gherkin. 
Control: Same as for (1) Fungus Leaf 



Spot except use sprays or dusts containing 
copper or streptomycin or a combination 
of both. See under the plant involved. 
(3) Leaf Blight, Leaf Blotch, Anthracnose 

(A term originally associated with diseases 
caused by certain types of fungi.) , Needle 
Blight, or Cast of Evergreens Leaves often 
suddenly and conspicuously spotted. Spots 
often later enlarge and usually become 
angular to irregular in shape. Affected 
leaves and stems often wilt, wither, die, 
and may fall prematurely. Fruit may sun- 
scald. Stems and twigs may die. Tops of 
vegetables and flowers may be killed. See 

(21) Crown Rot and (24) Fire Blight. 
Plants Attacked: Abutilon, African daisy, 
allium, almond, alternanthera, amaranth, 







Fig. 16. Bacterial leaf spots and blights. A. Bacterial blight of bean, B. Bacterial leaf 
spot of begonia, C. Delphinium black blotch, D. Bacterial blight of English walnut. 



36 



GENERAL DISEASES 





NORWAY MAPLE 





17. Leaf blights. A. Early blight of tomato. B. Anthracnose of Norway and sugar 
maples. C. Late blight of celery. D. Leaf blight of phlox. 



amaryllis, Amazon-1 i 1 y , amelanchier, 
apple, apricot, arborvitae, arbutus, arcto- 
tis, artemisia, ash, asparagus, asparagus- 
fern, aspidistra, aster, aucuba, avocado, 
azalea, balloonflower, balsam-apple, bal- 
sam-pear, barberry, bean, beet, begonia, 
bentgrass, Bermudagrass, birch, black- 
berry, blueberry, blue-eyed grass, blue- 
grass, Boston ivy, buffalograss, boxelder, 
boxwood, boysenberry, broom, butter-and- 
eggs, buttercup, butterfly-flower, butter- 
nut, buttonbush, cabbage, cacti, caesal- 
pinia, calendula, California-laurel, calla, 
camellia, camphor-tree, cantaloup, cape- 
cow s 1 i p, cape-honeysuckle, carnation, 
carpetgrass, carrot, cassaba, cassabana, 



castorbean, catalpa, cauliflower, celery, 
celeriac, centipedegrass, centuryplant, ceri- 
man, chamaecyparis, chayote, cherry, 
cherry-laurel, chestnut, chicory, China- 
aster, Chinese cabbage, Chinese evergreen, 
Chinese waxgourd, Christmas-rose, 
chrysanthemum, cinnamon-tree, citron, 
clarkia, clematis, cockscomb, collards, 
coralberry, coriander, corn, cosmos, coton- 
easter, crabapple, crapemyrtle, crassula, 
crinum, croton, cryptomeria, cucumber, 
currant, curuba, cyclamen, cypress, daffo- 
dil, dahlia, daisy, daphne, daylily, del- 
phinium, dewberry, dieffenbachia, dog- 
wood, Douglas-fir, dracaena, eggplant, elm, 
endive, English ivy, erythronium, euony- 



GENERAL DISEASES 



37 



mus, European cranberry-bush, fall daffo- 
dil, false-garlic, feijoa, ferns, fescue grass, 
fig, fir, flowering currant, flowering 
quince, forsythia, foxglove, garden cress, 
garlic, gentian, geranium, gherkin, giant 
sequoia, ginkgo, gladiolus, gloxinia, goose- 
berry, gourds, grape, grapefruit, guava, 
Guernsey-lily, hackberry, hardy orange, 
hawthorn, heliopsis, hemlock, hen-and- 
chickens, hibiscus, hickory, holly, holly- 
hock, honeysuckle, horsechestnut, horse- 
radish, hosta, houseleek, huckleberry, in- 
cense-cedar, India rubber tree, iris, Jack- 
in-the-pulpit, Japanese plum-yew, Japan- 
ese quince, jetbead, juniper, larch, kerria, 
larkspur, lavatera, leek, lemon, lemon- 
verbena, lettuce, lilac, lily, lily-of-the- 
valley, lime, linden, lippia, locust, London 
plane, loosestrife, loquat, lupine, lycoris, 
madrone, mallow, maple, Mayapple, med- 
lar, mignonette, mint, mitella, mock- 
cucumber, montbretia, mountain-a s h , 
mountain-laurel, muskmelon, mustard, 
nandina, narcissus, nectarine, nephthytis, 
nightshade, oak, okra, oleander, olive, 
onion, orange, orchids, Oregon-grape, 
osage-orange, pachysandra, palms, pansy, 
parsley, parsnip, pawpaw, pea, peach, 
pear, pea-tree, pecan, peony, peperomia, 
pepper, persimmon, petunia, philoden- 
dron, phlox, photinia, pine, pinks, pis- 
tachio, planetree, plum, poinciana, poin- 
settia, pomegranate, poplar, potato, po- 
tentilla, primrose, privet, pumpkin, pyra- 
cantha, pyrethrum, quince, radish, rape, 
raspberry, redcedar, redtop, redwood, 
retinospora, rhododendron, rhubarb, rose, 
roselle, rosemallow, rutabaga, ryegrass, 
safflower, St. Augustine grass, salal, sal- 
piglossis, salsify, scarborough-lily, scarlet 
runner bean, sedum, sequoia, shallot, 
Shasta daisy, sicana, snapdragon, snowball, 
snowberry, snowdrop, snowflake, soap- 
berry, spiderlily, spinach, spruce, squash, 
stock, strawberry, sugarberry, sweetpea, 
sweetpotato, sweet-william, sycamore, tan- 
bark-oak, toadflax, tomato, tritonia, trum- 
petvine, tuberose, tulip, tupelo, turnip, 
udo, vegetable-marrow, viburnum, Vir- 
ginia-creeper, vinca, violet, wallflower, 
walnut, waterlily, watermelon, wheatgrass, 
willow, yam, yew, yucca, zephyranthes, 
zinnia, and zoysiagrass. 
Control: Same as for (1) Fungus Leaf 
Spot. Prune trees and shrubs for better 
air circulation. 

(4) Shot-hole Small spots on leaves of 
stone fruits and related plants which later 
drop out leaving typical shot-holes. In- 



fected leaves often change color and drop 
prematurely. Young fruit may be spotted, 
deformed, and fall early. Sunken, reddish 
cankers may develop on the twigs. Fruit 
buds and fruiting wood may die during 
the winter. Shot-hole may be caused by 
bacteria, fungi, viruses, or spray injury. 
It is often a secondary symptom of fungus 
or bacterial leaf spot on many kinds of 
plants. See (1) Fungus Leaf Spot and (2) 
Bacterial Leaf Spot above. 
Plants Attacked: Almond, apricot, cherry, 
cherry-laurel, flowering almond, flowering 
cherry, nectarine, peach, and plum. 
Control: Same as for (1) Fungus Leaf 
Spot. Follow spray progam for fruits in 
question as given in Table 10 in the Ap- 
pendix. Collect and burn fallen leaves, 
w r here possible. Plant virus-free stock from 
a reliable nursery. 

(5) Botrytis Blight, Gray-mold Blight, Bud 
Rot, Blossom Blight, Twig Blight Generally 
distributed. Soft, tan-colored to brown 
spots or blotches on leaves, stems, flowers, 
ripening fruit, tubers, or roots during or 
following cool, damp periods. Affected 
parts are often covered with a coarse, tan- 
nish-gray mold in damp weather. Seedlings 
or young shoots may wilt and collapse if 
attacked near the soil line. Buds may rot. 
Flowers may be distorted with irregular 
flecks or spots. Older flowers rot quickly. 
Common in greenhouses and cool, humid 
areas. See (31) Flower Blight and (32) 
Fruit Spot. The fungus enters through 
wounds, dying leaves, or old flower petals. 
Plants Attacked: African-violet, alder, al- 
mond, amaryllis, Amazon-lily, anemone, 
apple, apricot, arborvitae, aristolochia, 
artemisia, artichoke, ash, asparagus, aster, 
aucuba, azalea, babysbreath, barberry, 
bean, beet, begonia, blackberry, blood- 
root, blueberry, blue cohosh, boysenberry, 
broccoli, Brussels sprouts, buttercup, cab- 
bage, cacti, caladium, calendula, calla, 
camass, camellia, candytuft, cape-mari- 
gold, carnation, carrot, castorbean, cauli- 
flower, celery, centuryplant, cherry, chic- 
ory, China-aster, Chinese hibiscus, chives, 
Christmas-rose, chrysanthemum, cigar- 
flower, cineraria, clarkia, colchicum, col- 
eus, columbine, coralberry, cornflower 
aster, cotton-rose, cranesbill, cucumber, 
currant, cyclamen, dahlia, daphne, day- 
lily, delphinium, dewberry, dogwood, 
dogstooth-violet, Douglas-fir, dracaena, 
dusty-miller, Dutchmans-pipe, eggplant, 
endive, English daisy, escarole, eupato- 
rium, European cranberry-bush, exacum, 



38 



GENERAL DISEASES 




PEACH 




CHERRY 



Fig. 18. Shot-hole of peach and cherry. These same leaf symptoms may be caused by 
various fungi, bacteria, viruses, or pesticide injury. 



feijoa, fennel, fig, flax, flowering almond, 
flowering currant, forget-me-not, fuchsia, 
gardenia, garlic, gentian, geranium, glad- 
iolus, globe-amaranth, globe artichoke, 
gloxinia, godetia, gooseberry, grape, gyp- 
sophila, hawthorn, heath, heliotrope, hem- 
lock, honeysuckle, hyacinth, hydrangea, 
iris, ixia, Jack-in-the-pulpit, kale, kohl- 
rabi, larch, leek, lentil, lettuce, lilac, lily, 
lily-of-the-valley, lobelia, lupine, Maltese 
cross, marigold, Mayapple, mertensia, 
mistflower, mockorange, narcissus, nastur- 
tium, okr?., onion, orchids, pansy, parsnip, 



pea, peach, peanut, pear, peony, pepper, 
persimmon, petunia, phlox, pine, pinks, 
plantainlily, plum, poinsettia, pomegran- 
ate, poppy, potato, primrose, pumpkin, 
pyrethrum, quince, rape, raspberry, red- 
wood, rhododendron, rhubarb, rockcress, 
rose, roselle, rose-of-Sharon, rutabaga, saf- 
flower, sea-lavender, sequoia, shallot, 
skullcap, snapdragon, snowberry, snow- 
drop, snow-on-the-mountain, spruce, 
squash, statice, stock, stokesia, strawberry, 
sunflower, sweetpea, sweetpotato, thimble- 
berry, tomato, tradescantia, Transvaal 



GENERAL DISEASES 



39 



daisy, tuberose, tulip, turnip, verbena, 
viburnum, vinca, violet, Virginia blue- 
bell, wallflower, and zinnia. 
Control: Cut and burn infected plants 
and plant parts, where practical. Carefully 
remove and burn fading flowers before 
petals fall. Avoid overcrowding, wet 
mulches, and shady or low spots with 
poor air circulation. Keep down weeds. 
Cure bulbs, corms, tubers, etc., rapidly at 
high temperatures before storing at the 
recommended temperature. Avoid high 
humidities indoors. Increase air circula- 



tion and temperature. Keep water off the 
foliage when watering. Spray at 5-day 
intervals during cool, wet weather using 
captan, zineb, ferbam, thiram, maneb, 
chloranil, phaltan, dichlone, or a copper- 
containing fungicide. Take cuttings from 
healthy plants and propagate in a steri- 
lized rooting medium. Spray flowers just 
before storage using zineb or captan (2/ 3 
tablespoon per gallon) . 
(6) Downy Mildew Pale green or yellow- 
ish areas usually appear on the upper leaf 
surface with corresponding light gray, 






Fig. 19. Botrytis blight or gray-mold blight. A. Geranium, B. Peony, C. Lily, D. Aster. 
Note gray mold on peony bud and aster stem. 



40 GENERAL DISEASES 




Fig. 20. Downy mildew. A. Grape, B. Lettuce, C. Cucumber, D. Spinach. 



downy, or purplish patches of mildew be- 
low. Affected areas enlarge and turn yel- 
low or brown. Leaves often wilt, wither, 
and die early. Stems, flowers, and fruits 
are sometimes infected. Seedlings may 
wilt and collapse. Attacks are most severe 
in cool, humid, or wet weather (warm 
days and cool nights) . 
Plants Attacked: Acalypha, ampelopsis, 
anemone, arrowwood, artemisia, artichoke, 
aster, avens, bachelors-button, balsam- 
apple, balsam-pear, bean, bedstraw, beet, 
Bermudagrass, blackberry, Boston ivy, 
boysenberry, broccoli, Brussels sprouts, 
bryonopsis, butter-and-eggs, buttercup, 
butternut, cabbage, caladium, candytuft, 



cantaloup, carnation, carrot, cassaba, caul- 
iflower, celery, celtuce, centaurea, chervil, 
chicory, China-aster, chinaberry, Chinese 
cabbage, Chinese waxgourd, chives, cine- 
raria, citron, clarkia, collards, cornflower, 
cornflower aster, corydalis, cranesbill, 
crimson daisy, crownbeard, cucumber, 
currant, damesrocket, dewberry, dragon- 
head, Dutchmans-breeches, eggplant, en- 
dive, erysimum, escarole, eupatorium, 
European cranberry-bush, evening-prim- 
rose, everlasting flower, false-dragonhead, 
fennel, fleabane, flowering tobacco, forget- 
me-not, four-o'clock, gaillardia, garden 
cress, garlic, germander, gilia, godetia, 
goldenglow, gooseberry, gourds, grape, 



GENERAL DISEASES 



41 



hackberry, herons-bill, horseradish, 
houndstongue, houstonia, Jerusalem-arti- 
choke, Joe-pye-weed, kale, kohlrabi, leek, 
lettuce, liverleaf, lupine, marigold, mead- 
owrue, meconopsis, melothria, mertensia, 
mignonette, mock-cucumber, monkshood- 
vine, mullein, muskmelon, mustard, nico- 
tiana, onion, pansy, parsley, parsnip, pea, 
pecan, pepper, peppergrass, phlox, physo- 
stegia, poppy, potentilla, prairie-cone- 
flower, prickly-poppy, primrose, privet, 
pumpkin, radish, raspberry, redbud, rhu- 
barb, rockcress, rockjasmine, rose, rud- 
beckia, rutabaga, salvia, sand-verbena, 
shallot, silene, silphium, snapdragon, 
snowberry, speedwell, spiderflower, spin- 
ach, squash, squirrelcorn, stock, straw- 
berry, sugarberry, sunflower, sweet alys- 
sum, sweetpea, Swiss chard, teasel, toad- 
flax, tomato, toothwort, trailing four- 
o'clock, turnip, umbrellawort, verbena, 
viburnum, violet, Virginia-creeper, wall- 
flower, walnut, watermelon, wayfaring- 
tree, West Indian gherkin, whitlowgrass, 
and wild sweet-william. 
Control: Practice a 2- to 3-year crop ro- 
tation. Collect and burn infected plant 
parts when first evident. Burn tops after 
harvest. Maintain a balanced soil fertil- 
ity, based on a soil test. Use disease-free 
seed from healthy stock plants. Resistant 
varieties offer hope for some types. Avoid 
overcrowding and high humidities indoors 
and in the seedbed. Dust or spray at 5- 
day intervals in cool, wet weather using 
a zineb, maneb, chloranil, or copper-con- 
taining fungicide. Or follow the spray 
schedule outlined under plant in ques- 
tion. 

(7) Powdery Mildew Supeficial, white to 
light grayish, powdery coating or felt on 
leaves, buds, flowers, and young shoots. 
Affected plant parts may be dwarfed and 
curled. Leaves may yellow, wither, and 
die prematurely. Mildew spots often en- 
large until they eventually cover the 
whole leaf. Common when cool nights fol- 
low warm days, in crowded low areas 
where air circulation is poor, or in damp, 
shaded locations. Powdery mildew is most 
common on many plants from mid- 
summer on. 

Plants Attacked: Abelia, acacia, acalypha, 
acanthopanax, achillea, aconitum, Afri- 
can-violet, ageratum, alder, almond, 
amelanchier, amorpha, ampelopsis, an- 
chusa, anemone, anoda, apple, apricot, 
aralia, arenaria, arnica, arrowwood, arte- 



misia, artichoke, artillery-plant, ash, aspar- 
agus-bean, aster, astilbe, aucuba, avens, 
avocado, azalea, baby tears vine, bach- 
elors-button, balsam-apple, balsam-pear, 
balsamroot, barberry, basketflower, bean, 
bearberry, bedstraw, beech, beet, begonia, 
bellflower, Bermudagrass, betony, birch, 
bishopscap, bittersweet, blackberry, black 
locust, bladder-senna, blazing-star, blue- 
berry, blue daisy, bluegrass, boltonia, 
Boston ivy, boxelder, boysenberry, broc- 
xoli, broom, buckthorn, buffaloberry, 
bur-marigold, burnet, buttercup, butter- 
fly-flower, buttonbush, cabbage, calendula, 
California-poppy, California-rose, calycan- 
thus, campanula, camphor-tree, candytuft, 
cantaloup, Canterbury-bells, cardoon, car- 
nation, carrot, cassia, catalpa, cauliflower, 
centaurea, cherry, cherry-laurel, chestnut, 
chicory, China-aster, chinaberry, Chinese 
cabbage, chinquapin, chrysanthemum, 
cigarflower, cineraria, citron, clematis, col- 
lards, collomia, columbine, coralbells, 
coralberry, coreopsis, cornflower, corn- 
salad, cosmos, cotoneaster, cottonwood, 
crabapple, cranesbill, crapemyrtle, crimson 
daisy, crotalaria, crownbeard, cucumber, 
culversroot, currant, dahlia, delphinium, 
dewberry, dogwood, dusty-miller, dwarf 
cornel, eggplant, elder, elecampane, elm, 
endive, erysimum, euonymus, eupatorium, 
European cranberry-bush, evening-prim- 
rose, false-indigo, fescue grass, feverfew, 
filbert, filipendula, fleabane, flowering al- 
mond, flowering raspberry, flowering to- 
bacco, foamflower, forestiera, forget-me- 
not, fringetree, fuchsia, gaillardia, gar- 
denia, gaultheria, geranium, germander, 
gilia, globe artichoke, globemallow, glow- 
ing gold, golden-aster, goldenglow, goose- 
berry, gourds, grape, groundsel, hackberry, 
hardhack, hawksbeard, hawthorn, hazel- 
nut, heath, heliopsis, heuchera, hickory, 
highbush cranberry, holly, hollyhock, 
holodiscus, honeylocust, honeysuckle, hop- 
hornbeam, hoptree, hornbeam, horse- 
chestnut, horseradish, houndstongue, 
huckleberry, hyacinth-bean, hydrangea, 
hypericum, indigo, indigobush, inula, 
Japanese pagodatree, Jerusalem-artichoke, 
Joe-pye-weed, kalanchoe, kale, kohlrabi, 
Labrador-tea, leopardsbane, lettuce, lia- 
tris, lilac, linden, lithospermum, locust, 
London plane, lupine, lyonia, magnolia, 
mallow, maple, marguerite, matricaria, 
matrimony-vine, Mayflower, meadowrue, 
meadowsweet, meconopsis, melothria, 
menziesia, mertensia, mint, mistflower. 




Fig. 21. Powdery mildew. A. Zinnia, B. Rose, C. Lilac, D. Phlox. The black specks in the 

left phlox leaf are the sexual fruiting bodies (cleistothecia) of the powdery mildew 

fungus. These are often produced on plants late in the growing season. 



GENERAL DISEASES 



43 



mitella, mock-cucumber, mockorange, 
monkeyflower, monkshood-vine, moon- 
seed, mountain-ash, mountain-h oily, 
mountain-laurel, mountain-mint, mul- 
berry, mullein, muskmelon, mustard, 
myrtle, nectarine, nemophila, New 
Jersey-tea, nicotiana, ninebark, oak, 
okra, orange, osoberry, oxalis, painted- 
cup, painted-tongue, pansy, parsnip, pea, 
peach, pear, pecan, penstemon, peony, 
pepper, persimmon, petunia, phacelia, 
philibertia, phlox, photinia, piggy-back 
plant, piqueria, planetree, plum, plumed 
thistle, polemonium, poplar, poppy, 
potato, potentilla, prairie-coneflower, 
prickly-ash, primrose, privet, prunella, 
pumpkin, purple-flowered groundcherry, 
queen-of-the-prairie, quince, radish, rape, 
raspberry, rhododendron, rose, roselle, 
rose-moss, rudbeckia, rue-anemone, ruta- 
baga, St. -Johns-wort, salal, salpiglossis, 
salsify, salvia, sandwort, sarsaparilla, sassa- 
fras, saxifrage, scabiosa, scarlet runner 
bean, senna, serviceberry, silphium, silver- 
berry, silver king, skullcap, snapdragon, 
sneezeweed, snowball, snowberry, snow- 
on-the-mountain, soapberry, sophora, 
speedwell, spirea, spurge, squash, stachys, 
strawberry, sumac, sunflower, swede, sweet 
alyssum, sweetpea, sycamore, tamarisk, 
tansy, teasel, tepary bean, thermopsis, 
thistle, tickseed, tidytips, tomato, trailing- 
arbutus, trailing four-o'clock, Transvaal 
daisy, tree-tomato, trumpetvine, tuliptree, 
turnip, turtlehead, valerian, verbena, 
viburnum, violet, Virginia bluebell, Vir- 
ginia-creeper, wallflower, walnut, water- 
melon, weigela, West Indian gherkin, 
wheatgrass, wild sweet-william, willow, 
winterberry, wisteria, witch-hazel, wolf- 
berry, woodwaxen, yellow ironweed, yel- 
lowwood, and zinnia. 
Control: Resistant varieties of certain 
flowers and vegetables are available. 
Avoid overcrowding and damp, shady lo- 
cations. Indoors, increase air circulation 
and night temperature. Where needed, 
dust or spray several times, 7 to 10 days 
apart, using Karathane, sulfur, Acti-dione, 
or phaltan. Avoid applications when the 
temperature is 85° F. or above. Collect 
and burn affected leaves, stems, and other 
debris in the fall. 

(8) Rust - Leaf, Stem, Needle Bright yel- 
low, orange, orange-red, reddish-brown, 
chocolate-brown, or black powdery pus- 
tules. Some rusts have as many as five 



different spore forms in a single season's 
life cycle which vary in size, shape, and 
color. Pustules are most common on the 
lower leaf surface and on stems. Leaves 
often wither and die early; plants may be 
stunted. When severe, they may even wilt 
and die (e.g., snapdragon) . 

True rusts are of two general types: 

(a) Fungus completes life cycle on the 
same type of plant (autoecious or monoec- 
ious rusts) . Examples: Asparagus, bean, 
beet, blackberry, carnation, chrysanthe- 
mum, hollyhock, pea, raspberry, rose, 
snapdragon, sunflower, Swiss chard, and 
violet. 

(b) Fungus requires two different 
kinds of plants, (or an alternate host) to 
complete the life cycle. Such rusts are 
heteroecious. Examples: 

1. Juniper or redcedar and apple, 
chokeberry, crabapple, quince, 
flowering quince, mountain-ash, 
hawthorn, photinia, amelanchier, 
squaw-apple, fendlera, mockorange, 
etc. 

2. Spruce and bog-rosemary, creeping 
snowberry, Labrador-tea, pyrola, 
woodnymph, crowberry, rhododen- 
dron, etc. 

3. Pine and bellflower, goldenrod, 
sunflower, moonflower, Jerusalem- 
artichoke, morning-glory, moon- 
flower-vine, quamoclit, gaillardia, 
currant, gooseberry, blazing-star, 
marigold, senecio, China-aster, vi- 
burnum, Indian paintbrush, sweet- 
fern, sweetgale, oak, buckleya, am- 
sonia, sweetpotato, etc. 

4. Hemlock and poplar, blueberry, 
azalea, rhododendron, menziesia, 
hydrangea, lyonia, etc. 

5. Douglas-fir and poplar. 

6. Larch and willow, poplar, or birch. 

7. Lupine and spinach, garden cress, 
and radish. 

8. Currant and gooseberry and carex, 
willow, etc. 

9. Wild grasses and aconite, anemone, 
barberry, beet, buckthorn, Cali- 
fornia-bluebell, clematis, colum- 
bine, coralberry, delphinium, flea- 
bane, four-o'clock, garden cress, 
heliotrope, Indian paintbrush, 
meadowrue, mertensia, mint, prim- 
rose, queens-delight, radish, sand 



44 GENERAL DISEASES 




UPPER SIDE 



SPRING 



Fig. 22. Rust. A. Snapdragon, B. Bean, C. Apple, D. Juniper. The rust on juniper and 
apple (cedar-apple rust) are different disease symptoms caused by the same rust 

fungus. 



verbena, snowberry, spiderflower, 
spinach, turtlehead, wolfberry, etc. 

10. Corn and oxalis. 

11. Fir and ferns, willow, huckleberry, 
blueberry, chickweed, birch, etc. 

Rust on juniper and redcedar appears 
as reddish-brown, bean-shaped galls from 
which protrude a mass of orange, gelat- 



inous tendrils during spring rains (Fig- 
ure 22D) . 

Plants Attacked: Abutilon, acacia, acan- 
thopanax, achillea, aconitum, ageratum, 
alder, allium, almond, amelanchier, Amer- 
ican spikenard, amorpha, ampelopsis, am- 
sonia, anchusa, anemone, angelica, anise, 
anise-root, anoda, apple, apricot, aralia, 



GENERAL DISEASES 



45 



arbutus, arenaria, armeria, arnica, arrow- 
wood, artemisia, ash, asparagus, aster, 
atamasco-lily, avens, azalea, babysbreath, 
baby tears vine, bachelors-button, balsam- 
root, baneberry, barberry, bayberry, bean, 
bearberry, bedstraw, beet, bellflower, bell- 
wort, bentgrass, Bermudagrass, birch, 
bishopscap, blackberry, black gum, blad- 
der-senna, blazing-star, blueberry, blue- 
eyed grass, bluegrass, boisduvalia, bol- 
tonia, bouvardia, boysenberry, brodiaea, 
broom, buckthorn, buffaloberry, buffalo- 
grass, bur-marigold, burnet, buttercup, 
butterflyweed, buttonbush, caesalpinia, 
calendula, California-bluebell, California- 
rose, calochortus, campion, canna, Canter- 
bury-bells, cape-marigold, cardinal 
climber, carnation, carpetgrass, carrot, 
centaurea, chamaecyparis, chamaedaphne, 
checkermallow, cherry, chicory, China-as- 
ter, Chinese lanternplant, chives, choke- 
berry, chrysanthemum, chuperosa, cimici- 
fuga, cissus, clarkia, clematis, coffeeberry, 
collinsia, collomia, columbine, columbo, 
coralbells, coralberry, corn, cornel, corn- 
flower, corydalis, cosmos, Cottonwood, 
cowania, crabapple, cranesbill, crimson 
daisy, crownbeard, culversroot, cunila, 
currant, cypress, cypress-vine, dayflower, 
delphinium, desertplume, dewberry, dit- 
tany, Douglas-fir, dogwood, dogstooth-vi- 
olet, Dutchmans-breeches, dwarf cornel, 
dyschoriste, echeveria, eggplant, elder, ele- 
campane, emilia, encelia, endive, erysi- 
mum, eupatorium, evening-primrose, 
false-dragonhead, false-garlic, false-indigo, 
false-mesquite, fendlera, ferns, fescue 
grass, fig, fir, flax, fleabane, filipendula, 
Florida yellowtrumpet, flowering currant, 
flowering quince, flowering raspberry, 
foamflower, forestiera, forget-me-not, four- 
o'clock, frangipani, fritillaria, fuchsia, 
gaillardia, garden cress, garlic, gentian, 
geranium, germander, giant night white 
bloomer, gilia, globemallow, godetia, gold- 
en-aster, goldenglow, gooseberry, grape, 
groundcherry, ground-pink, groundsel, 
harebell, hawksbeard, hawthorn, hearts 
and honey vine, heath, heliopsis, helio- 
trope, hemlock, hen-and-chickens, Hercu- 
les-club, heuchera, hibiscus, holly, holly- 
hock, honeylocust, honeysuckle, hophorn- 
beam, hoptree, horsechestnut, houseleek, 
houstonia, huckleberry, hyacinth, hydran- 
gea, hypericum, incense-cedar, indigobush, 
iris, Jack-in-the-pulpit, jacquemontia, Je- 
rusalem-artichoke, Joe-pye-weed, juniper, 
kochia, Labrador-tea, lantana, larch, lava- 



tera, leadtree, leatherwood, leek, leonotis, 
lettuce, liatris, lily, lithospermum, liver- 
leaf, lobelia, locust, loosestrife, lupine, ly- 
onia, madrone, mahonia, malacothrix, 
mallow, Maltese cross, malvastrum, man- 
freda, mangel, manzanita, maranta, mar- 
bleseed, marigold, matricaria, matrimony- 
vine, mayapple, meadowrue, meadow- 
sweet, mentzelia, menziesia, mertensia, 
mistflower, mitella, mockorange, monarda, 
monardella, monkeyflower, monkshood, 
moonflower, morning-glory, mountain-ash, 
mustard, nasturtium, New Jersey-tea, oak, 
okra, onion, orchids, Oregon-grape, Osage- 
orange, osier, oxalis, painted-cup, pansy, 
pea, peach, peanut, pear, pearleverlasting, 
penstemon, peppergrass, petunia, pha- 
celia, philibertia, phlox, photinia, physo- 
stegia, pine, pinks, plum, plumed thistle, 
poinciana, poinsettia, polemonium, poly- 
gala, poplar, poppy-mallow, potentilla, 
prairie-coneflower, primrose, prickly-ash, 
prickly-poppy, prune, quamoclit, queen- 
of-the-prairie, queens-delight, quince, rad- 
ish, rainlily, raspberry, redcedar, redtop, 
rhododendron, rhubarb, rockcress, rock- 
jasmine, romanzoffia, rose, rosemallow, 
rose-of-Sharon, rougeplant, rudbeckia, rue- 
anemone, ruellia, Russian-olive, ryegrass, 
safflower, St. -Andrews-cross, St. Augustine 
grass, St. -Johns-wort, salsify, salvia, sand- 
verbena, sarsaparilla, satin-flower, saxi- 
frage, scarlet runner bean, sea-lavender, 
sedum, sensitive plant, shallot, shooting- 
star, sida, sidalacea, silphium, silverberry, 
silver king, silver lacevine, smelowskia, 
smoketree, snapdragon, sneezeweed, snow- 
berry, snow-on-the-mountain, sophora, 
southern leatherwood, speedwell, spider- 
flower, spinach, spruce, spurge, stanleya, 
stachys, statice, stenanthium, sumac, sun- 
flower, sweetfern, sweetgale, sweet-jarvil, 
sweetpea, sweetpotato, sweet-william, Swiss 
chard, synthyris, taenidia, tamarack, tan- 
bark-oak, tansy, tepary bean, thimbleberry, 
thistle, tickseed, toadflax, toothwort, 
tradescantia, trailing four-o'clock, trillium, 
trumpettree, tupelo, turtlehead, valerian, 
venus-lookingglass, verbena, viburnum, 
vinca, violet, watercress, waxmyrtle, wheat- 
grass, white-cedar, whitlowgrass, wild 
sweet-william, willow, wirelettuce, wolf- 
berry, woodwaxen, wyethia, yellow-cedar, 
yellow ironweed, yerba-buena, yucca, zau- 
schneria, and zephyranthes. 
Control: If possible, destroy nearby alter- 
nate host plants, especially weeds which 
show rust. A distance of several hundred 








si 






III 



Mil 



*^^^^^n^^^B 





Fig. 23. White-rust. A. Cabbage, B. Horseradish, C. Spinach, D. Radish 

flower parts. 




GENERAL DISEASES 



47 



yards between alternate hosts, or more, is 
usually necessary for some measure of 
control. Collect and burn infected plant 
parts when first seen. Follow a spray pro- 
gram for fruits (see Table 10 in the Ap- 
pendix) and certain flowers. Dust or spray 
with ferbam, zineb, maneb, or sulfur. 
Prune out and burn infected tree 
branches showing rust cankers, galls, 
spindle-shaped swellings, or witches'- 
brooms. Use resistant varieties or species 
when available. Plant only healthy stock. 
Where rust is perennial in roots (e.g., 
orange rust of bramble fruits) , destroy 
plants before pustules appear in the 
spring. Indoors, raise the temperature, re- 
duce air humidity, and keep water off the 
foliage. 

(9) White-Rust, White Blister Pale yellow 
areas develop on the upper leaf surface 
with whitish pustules which may turn pale 
yellow with age forming on the corre- 
sponding underside of the leaves. The 
yellowish areas later turn brown and in- 
fections may spread to stems and flowers 
causing malformation and abortion. 
Leaves may eventually die and plants are 
dwarfed. 

The white rusts are not related to the 
true rusts above. 

Plants Attacked: Alternanthera, alyssum, 
amaranth, antennaria, artemisia, bach- 
elors-button, beet, black-salsify, broccoli, 
Brussels sprouts, cabbage, California-rose, 
candytuft, cardinal climber, cauliflower, 
centaurea, Chinese cabbage, cornflower, 
cypressvine, damesrocket, erysimum, eupa- 
torium, false-camomile, feverfew, four- 
o'clock, froelichia, garden cress, giant 
night white bloomer, globe-amaranth, 
groundsel, hearts and honey vine, horse- 
chestnut, horseradish, jacquemontia, kale, 
lettuce, matricaria, moonflower, morning- 
glory, mustard, parsnip, peppergrass, 
plumed thistle, quamoclit, radish, rock- 
cress, rose-moss, rutabaga, salsify, scurvy- 
weed, spinach, stock, sunflower, sweet 
alyssum, sweetpotato, thistle, toothwort, 
trailing four-o'clock, turnip, umbrella- 
wort, wallflower, watercress, and whitlow- 
grass. 

Control: Collect and burn infected plant 
parts. Destroy tops after harvest. Destroy 
nearby cruciferous weeds such as mus- 
tards, lambsquarters, and pigweed. Spray 
plants several times, 10 to 14 days apart, 
with maneb or a copper-containing fung- 
icide. 



(10) Leaf Curl or Gall, Leaf Blister, 
Witches'-brocm, Plum Pockets Conspicuous 
white, yellow, red, brown, or gray "blis- 
ters" on leaves. Leaves may become puffy, 
puckered, thickened, and curled. Tend to 
drop early. Often fail to set fruit. Young 
peach fruit may be distorted and cracked. 
Plum fruits turn into enlarged swollen 
"bladders." Witches'-brooms (brushlike 
development of many weak shoots arising 
at or close to the same point) occur on 
cherry, plum, alder, birch, California 
buckeye, and rhododendron stems. 
Plants Attacked: Alder, almond, amel- 
anchier, apricot, azalea, bearberry, birch, 
blueberry, box sandmyrtle, buckeye, cam- 
ellia, cassiope, catalpa, chamaedaphne, 
cherry, cherry-laurel, chinquapin, cotton- 
wood, elm, ferns, filbert, flowering cherry, 
hazelnut, hophornbeam, hornbeam, 
huckleberry, lyonia, madrone, maple, nec- 
tarine, oak, peach, plum, poplar, rhodo- 
dendron, sumac, and willow. 

Control: Prune trees to increase air circu- 
lation. Remove witches'-brooms. Apply a 
single dormant spray to stone fruit trees 
before buds "break open" in the spring. 
Then follow the regular spray program 
during the season. See Table 10 in the 
Appendix and under the plant involved. 

(11) Smut — Leaf, Stem, Anther, and Seed 
Dark brown to black, sooty, spore masses 
formed inside swollen, whitish blisters or 
galls. Appear on leaves, stems, bulbs, 
flower parts, and seed. Affected parts may 
wither and die. Plants may be stunted. 
Many smut-producing fungi enter plants 
in the seedling stage and develop systemi- 
cally within the plant as it grows. The 
smut may not be evident externally until 
near maturity. Other smuts (e.g., corn 
and violet) are localized and any actively 
growing tissue (shoots, leaves, tassels, 
young ears, roots) may become infected. 
See (13) White Smut. 

Plants Attacked: Aconitum, anemone, 
arenaria, avens, baneberry, bentgrass, 
Bermudagrass, bloodleaf, bluegrass, buf- 
falograss, buttercup, camass, campion, 
carnation, chicory, chives, cissus, clematis, 
colchicum, columbine, coralbells, corn, 
cushion-pink, delphinium, dianthus, dogs- 
tooth-violet, ferns, fescue grass, fig, garlic, 
gilia, gladiolus, globeflower, grape-hya- 
cinth, hepatica, heuchera, leek, liverleaf, 
lupine, Maltese cross, meadowrue, men- 
ziesia, monkshood, onion, oxalis, pansy, 
plumed thistle, redtop, rue-anemone, rye- 



48 



GENERAL DISEASES 




DISEASED FRUITS 
NORMAL 1FRUIT SIZE 



Fig. 24. 



A. Witches'-broom of cherry. B. Peach leaf curl. C. Plum pockets. These diseases 
are all caused by very closely related fungi. 



grass, shallot, silver lacevine, speedwell, 
spurge, squill, sweet-william, thistle, tril- 
lium, venus-lookingglass, violet, and 
wheatgrass. 

Control: Pick off and burn infected parts 
before blisters open. Use disease-free 
transplants. Treat seed or plant resistant 
varieties, where available. See plant in 
question and Table 13 in the Appendix. 
(12) Sooty Mold or Blotch, Black Mildew 
Unsightly, superficial, dark brown or 
black blotches or coating on leaves, fruit, 
and stems. Can be removed easily by 
rubbing. Fungus usually grows on "honey- 
dew" excretions made by insects (e.g., 
aphids, scales, whiteflies, and others) or 
in flowing sap. Causes little if any damage 
to most plants. Subtropical plants, how- 
ever, are sometimes permanently dis- 
figured. 
Plants Attacked: Alder, American blad- 



dernut, anisetree, apple, arborvitae, ash, 
avocado, azalea, bearberry, beech, big- 
nonia, blackberry, blueberry, boxelder, 
buckthorn, buckwheat-tree, cacti, calen- 
dula, California-laurel, callicarpa, camel- 
lia, camphor-tree, catalpa, Carolina jes- 
samine, chinaberry, cimicifuga, clematis, 
coffeeberry, columbo, confederate-jasmine, 
cottonwood, crabapple, crapemyrtle, da- 
hoon, dewberry, dogwood, elm, English 
ivy, ferns, fig, fir, franklin-tree, gardenia, 
gaultheria, grapefruit, hawthorn, hazelnut, 
holly, huckleberry, hyacinth-bean, ice- 
plant, inkberry, juniper, lantana, leather- 
wood, lemon, lemon-verbena, leucothoe, 
lily, linden, lippia, lyonia, magnolia, man- 
zanita, maple, meconopsis, mockorange, 
oak, oleander, olive, onion, orange, os- 
manthus, palms, pansy, parkinsonia, 
partridge-berry, peach, pear, persimmon, 
philodendron, pine, plum, prickly-ash, 




HEALTHY 



Fig. 25. Smut. A. Corn, B. Onion. 




YOUNG 

DISEASED 





B \ C 

Fig. 26. Sooty mold on A. Magnolia, B. Apple, C. Basswood or Linden. 




50 



GENERAL DISEASES 



privet, redbay, redcedar, rhododendron, 
salal, sassafras, serviceberry, swampbay, 
sweetpotato, sycamore, tasseltree, tree-of- 
Heaven, tuliptree, twinflower, violet, wax- 
myrtle, willow, wintergreen, and yaupon. 
Control: Control insects by applying dusts 
or sprays containing malathion plus lin- 
dane, DDT, or methoxychlor. Check with 
your county agent, extension entomologist, 
florist, or nurseryman for the latest in- 
formation on insecticides. Follow the 
spray schedules for fruit given in Table 10 
in the Appendix. Avoid wounds. Paint in- 
jured areas promptly with a tree wound 
dressing (page 25) . 

(13) White Smut, Leaf Smut Pale, color- 
less, white, yellowish to yellowish-green 
leaf spots, which later turn a dark brown 
to black. Spots may sometimes drop out 




Fig. 27. White smut on calendula. 

leaving ragged holes. Usually a minor 
problem. Disease is apparently favored in 
some cases by acid soils and late planting. 
See also (11) Smut. 

Plants Attacked: Anemone, arnica, aster, 
bentgrass, bluegrass, boltonia, buttercup, 
butter-and-eggs, calendula, California- 
poppy, Chinese lanternplant, collinsia, 
crimson daisy, dahlia, delphinium, eryn- 
gium, eupatorium, frrewheel, fleabane, gail- 
lardia, goldenglow, groundcherry, ground- 
sel, lobelia, meadowrue, mertensia, moon- 
seed, pondlily, poppy, prairie-coneflower. 
redtop, rudbeckia, senecio, silphium, 
sneezeweed, speedwell, spinach, sunflower, 
treepoppy, Virginia bluebell, waterlily, 
and wood anemone. 

Control: Collect and burn diseased parts 
as they appear and burn plant debris after 
harvest. Spray with captan or a copper- 
containing fungicide at about 7- to 10-day 
intervals. Follow recommended cultural 
practices. 

(14) Scab Symptoms variable depending 
on plant. Usually appears as roughened, 
crustlike (often raised or sunken) areas 



on the surface of leaves, stem, fruit, root, 
tuber, or corm. Leaves may wither and 
drop early. Twigs often die back (willow) . 
Caused by a few bacteria and a wide range 
of fungi. Easily confused with certain leaf 
or fruit spots and blights. See (1) Fungus 
Leaf Spot, (3) Leaf Blight, and (32) 
Fruit Spot and Rot. 

Plants Attacked: Almond, apple, apricot, 
avocado, beet, cabbage, camphor-tree, can- 
taloup, carrot, cassaba, cherry, citron, 
cotoneaster, crabapple, crocus, cucumber, 
dahlia, eggplant, English ivy, euonymus, 
flowering cherry, freesia, gladiolus, gher- 
kin, gooseberry, grapefruit, guava, hardy 
orange, hawthorn, Hercules-club, hickory, 
honeydew melon, iris, jasmine, lemon, lima 
bean, lime, loquat, mangel, mountain-ash, 
muskmelon, nectarine, oleander, onion, 
orange, palms, pansy, parsnip, pea, peach, 
pear, pecan, persimmon, photinia, plum, 
poinsettia, poplar, potato, pumpkin, pyra- 
cantha, quince, radish, rape, rutabaga, 
salsify, snowberry, spinach, squash, sweet- 
potato, Swiss chard, tickseed, tigerflower, 
turnip, violet, walnut, watermelon, and 
willow. 
Control: 

A. For root crops — Use resistant varie- 
ties. Use disease-free tubers (potatoes) . 
Acidify the soil (to about pH 4.5) where 
practical. Avoid liming, applications of 
wood ashes, other alkaline materials, or 
barnyard manure. Practice a long crop ro- 
tation with nonsusceptible crops. Fertilize 
liberally. Keep down weeds. Turn under 
a green manure crop (page 16) where 
practical. 

B. For other vegetables — Long crop ro- 
tation. Treat seed (see Table 13 in the 
Appendix) ; plant resistant varieties; 
spray plants with zineb, maneb, ziram, or 
captan. 

C. For fruits and trees — Use resistant 
varieties if available. Remove and destroy 
dead twigs and branches and rotted fruit 
in the dormant season. Follow the spray 
program (Appendix, Table 14) using cap- 
tan, sulfur, zineb, or other fungicide. 

D. Flowers — Sanitation. Spray as for 
vegetables. Plant disease-free corms, tu- 
bers, bulbs, etc. See Table 13 in the Ap- 
pendix. 

(15) Wilts Wilting is due to a temporary 
or permanent deficiency of water in the 
foliage. Wilt diseases (causing permanent 
wilt) are easily confused with root rots, 
crown rots, stem cankers, grub or borer 



GENERAL DISEASES 



51 




Fig. 28. Scab. A. Potato, B. Peach, C. Apple, D. Cucumber. The name scab is given to 
diseases caused by entirely different organisms. Control measures also vary greatly. 



injury, drought, baking or compacting of 
the soil, etc. The over-all result is the 
same in all cases — a wilting, withering, 
and dying of the foliage beyond the point 
of injury. Only by close observation and 
experience can you determine the true 
cause. See under Stem and Root Diseases. 
Sprays or dusts are ineffective in control- 
ling wilts. 

There are three common types of wilts 
which may look identical, but are caused 
by altogether different organisms. These 
are Fusarium Wilt, Verticillium Wilt, and 
Bacterial Wilt. Wilt-producing fungi and 
bacteria invade the water and food-con- 
ducting vessels (vascular system) inside 
the stems and roots. The vessels become 
plugged and killed or become nonfunc- 
tional. The normal flow of liquids from 



the roots to the foliage is greatly decreased 
or stopped altogether. Wilting of infected 
branches then follows. 

Cutting into infected stems or branches 
commonly shows discolored streaks. Some 
plants die quickly from wilts; others may 
withstand attack for months or even years. 
For wilts which attack only a few plants, 
like Oak Wilt and Dutch elm disease, see 
under the plant involved. 
A. Fusarium Wilt or Yellows Plants are 
usually stunted and yellow. Disease 
symptoms often start at the base of the 
stem and progress upwards causing the 
leaves and flower heads to wilt and die. 
The lower parts of the stem (inside al- 
ways, outside sometimes) are dark and 
discolored. When stems are cut length- 
wise, brown to black streaks are evident 






Fig. 29. Fusarium wilt. A. Tomato, B. Cabbage (often called cabbage yellows), C. 
Watermelon, D. Aster. The inside of diseased stems shows dark streaks when cut (see 
cabbage insert) where the fusarium fungus causes a partial to complete stoppage of 
liquids in the water-conducting tissue. 



GENERAL DISEASES 



53 



inside. Infected seedlings wilt and col- 
lapse. See (21) Crown Rot. Nematodes 
often provide wounds by which the fusa- 
rium fungus may enter the roots. 
Plants Attacked: Alternanthera, aspara- 
gus, asparagus-fern, astilbe, bachelors-but- 
ton, bean, beet, bleedingheart, broccoli, 
browallia, Brussels sprouts, cabbage, 
cacti, cantaloup, cape-marigold, carnation, 
carrot, cassaba, catnip, cauliflower, celery, 
centaurea, China-aster, chrysanthemum, 
cineraria, citron, clarkia, collards, corian- 
der, cornflower, cosmos, crotalaria, cucum- 
ber, cyclamen, dahlia, daphne, delphin- 
ium, dill, eggplant, eupatorium, fig, fox- 
glove, freesia, garlic, gladiolus, groundsel, 
hebe, kale, kohlrabi, lantana, leek, mari- 
gold, "mimosa" tree, mock-cucumber, 
morning-glory, muskmelon, mustard, okra, 
orchids, painted-tongue, pansy, parsley, 
pea, peanut, pepper, petunia, poinsettia, 
polemonium, potato, pumpkin, radish, 
rutabaga, seakale, sedum, "smilax," snap- 
dragon, speedwell, spinach, squash, stock, 
sumac, sweetpea, sweetpotato, sweet-wil- 
liam, tomato, turnip, watermelon, and 
zinnia. 

Control: Use resistant varieties if avail- 
able: Aster, bean, cabbage, carnation, 
"mimosa" tree, muskmelon, pea, sweetpea, 
tomato, and watermelon. Treat seed or 
plant in disinfested soil (see tables 13 and 
14 in the Appendix) . Collect and burn 
infected plants. Practice a long crop rota- 
tion excluding members of the same plant 
family. Fertilize and water to encourage 
vigorous growth. 

B. Verticillium Wilt Leaves turn yellow 
and usually fall first from the lower part 
of the plant then the falling of the leaves 
progresses to higher parts of the plant. 
Infected trees and shrubs show one or 
more wilted branches with severe drop- 
ping of leaves from midsummer on. An- 
nual plants and young trees are often 
stunted, wilt, and usually die. Perennials 
may be killed or recover. Twigs and 
branches often die back. The internal 
wood tissues of infected stems show dark 
streaks (greenish, gray, yellowish-brown, 
brown, bluish-brown, purplish, or black) 
when cut lengthwise. Verticillium Wilt is 
more prevalent in cooler climates and at 
lower soil temperatures than Fusarium 
Wilt. Infections often occur through 
wounds. 



Plants Attacked: Abutilon, acanthopanax, 
aconitum, almond, American spikenard, 
apricot, aralia, artichoke, ash, asparagus, 
aspen, aster, aucuba, avocado, azalea, 
bachelors-button, balsam, barberry, bean, 
beech, beet, begonia, blackberry, black 
gum, black locust, blazing-star, boxelder, 
boysenberry, broccoli, Brussels sprouts, 
cabbage, calceolaria, California-poppy, 
camphor-tree, cantaloup, cape-marigold, 
carnation, cassaba, castorbean, catalpa, 
cauliflower, celery, centaurea, chayote, 
cherry, cherry-laurel, chicory, China-aster, 
chinaberry, Chinese lanternplant, chives, 
chrysanthemum, cineraria, citron, clarkia, 
coleus, collards, cornflower, crimson 
daisy, crown-of-thorns, cucumber, currant, 
dahlia, damesrocket, daphne, delphinium, 
dewberry, dogwood, eggplant, elder, elm, 
endive, erythrina, fleabane, foxglove, fre- 
montia, fuchsia, garlic, geranium, golden- 
rain-tree, grape, groundsel, heath, helio- 
trope, honeylocust, horsechestnut, horse- 
radish, Jerusalem-cherry, kale, Kentucky 
coffeetree, kohlrabi, leek, lettuce, liatris, 
lilac, linden, locust, magnolia, maple, 
marguerite, marigold, mignonette, mint, 
monkshood, muskmelon, mustard, New 
Zealand spinach, oak, okra, onion, Osage- 
orange, painted-tongue, parsley, pea, 
peach, peanut, peony, pepper, peppertree, 
persimmon, petunia, phlox, pittosporum, 
plum, polemonium, poplar, poppy, 
poppy-mallow, potato, privet, prune, 
pumpkin, quince, radish, raspberry, red- 
bud, rhubarb, rose, Russian-olive, rud- 
beckia, rutabaga, safflower, salsify, sassa- 
fras, scarlet eggplant, smoketree, snap- 
dragon, snowball, spinach, squash, stock, 
strawberry, strawflower, sumac, sunflower, 
sweetpea, sweetpotato, tickseed, Transvaal 
daisy, tuliptree, tomato, tree-of-Heaven, 
trumpetvine, turnip, udo, vegetable-mar- 
row, viburnum, walnut, watermelon, way- 
faring-tree, wildbergamot, and yellow- 
wood. 

Control: Dig up and burn infected 
flower, small fruit, and vegetable plants. 
Propagate from disease-free plants or use 
disease-free seed. Plant in clean or steri- 
lized soil (pages 437-44) which is well- 
drained. Control soil insects using aldrin, 
dieldrin, chlordane, etc. Practice a long 
crop rotation with nonrelated crops. 
Keep down weeds. Fertilize and water to 
encourage vigorous growth. Varieties of 







Fig. 30. Verticillium wilt. A. Eggplant, B. Tomato, C. Maple, D. Raspberry. Like Fu- 
sarium, the Verticillium wilt fungus plugs or otherwise disrupts the water-conducting 
tissue (see eggplant and maple). The result of this appears as dark streaks inside the 
stem. It is often difficult, without a microscopic examination, to tell which wilt-producing 
fungus is involved. 



GENERAL DISEASES 



55 



certain plants such as potato, strawberry, 
and tomato differ in resistance. For trees 
and shrubs: Remove wilted branches. 
Sterilize tools between cuts by dipping or 
swabbing in 70 per cent denatured alco- 
hol, then paint wound surfaces with a 
tree wound dressing (page 25) . 
C. Bacterial Wilt, Brown Rot, or Blight 
Symptoms variable. See under plant in- 
volved. Some plants show dark green, 
water-soaked areas in leaves which expand 
rapidly. Leaves then turn brown and dry. 
Sometimes a shiny "crust" or "scale" is 
evident on affected plant parts. Plants 
may be stunted, wilt suddenly or grad- 
ually, starting with some of the younger 
leaves, or there may be a slight yellowing 
of the older leaves. Stems often shrivel and 
dry out. A yellowish slime or water-soaked 
browning may be evident when the base 
of the stem is cut through and squeezed. 
Bacterial soft rot often follows in wet 
weather. See (29) Bacterial Rots. The 
wilt-producing bacteria enter through 
insect, nematode, and other mechanical 
wounds. 

Plants Attacked: Balsam, bean, beet, 
canna, cantaloup, carnation, carrot, cas- 
saba, castorbean, Chinese lanternplant, 
chrysanthemum, corn, cosmos, croton, 
cucumber, dahlia, delphinium, dieffen- 
bachia, eggplant, forsythia, geranium, 



gherkin, gourds, hibiscus, hollyhock, hy- 
drangea, lettuce, lilac, marigold, musk- 
melon, nasturtium, nicotiana, okra, pea, 
peanut, pepper, petunia, potato, pump- 
kin, rhubarb, squash, sunflower, sweet- 
potato, tomato, verbena, wallflower, water- 
melon, and zinnia. 

Control: Collect and burn infected plants. 
Control insects which may spread the 
disease using a mixture of methoxychlor 
or DDT and malathion. Resistant varieties 
are available for a few plants including 
cucumber, corn, carnation, and potato. 
Plant disease-free seed or treat before 
planting. See plant in question and Table 
13 in the Appendix. Long crop rotation 
(6 years or more) . Plant in well-drained, 
fertile soil, which is clean or sterilized. 
Indoors, raise temperature until disease 
is under control. Take cutting from 
healthy plants. 

(16) Mosaic, Mottle, Crinkle, Streak, Cal- 
ico, Visus Leaf Curl, Infectious Variegation, 
Flower Breaking This virus disease or com- 
plex shows variable symptoms. Most com- 
monly the leaves have a mild to severe 
yellowing or a pattern of light and dark 
green areas forming a mosaic or mottle. 
Sometimes yellowish or white, ring or 
line patterns or both may be seen. Leaves 
are commonly curled, distorted, puckered, 
crinkled, leathery, or even cupped sharply 




Fig. 31. Bacterial wilt. A. Corn, B. Cucumber. A sticky ooze is often evident when bacte- 
rial wilt-infected stems are cut and squeezed. 




HEALTHY 




DISEASED 





Fig. 32. Mosaic. A. Carnation, B. Tulip flower-breaking, C. Bean, D. Amaryllis 



GENERAL DISEASES 



57 



downward or upward. Leaf veins may be 
lighter than normal (cleared) or be 
banded with dark green or yellow areas. 

Flowers may be blotched or streaked 
with white or yellow, distorted, or fail to 
open normally. 

Plants may be stunted; fruit deformed, 
stunted, fewer in number, and usually 
lack flavor. Infected plants often show no 
external symptoms, especially at high tem- 
peratures (85° F. or above) . 

Mosaiclike diseases are commonly 
spread by many species of aphids, some 
by contact — all by propagation (grafting, 
budding, slips) from infected plants. 

Mosaics are often confused with plant 
nutrient deficiencies. 

Plants Attacked: Abutilon, aconitum, 
African-lily, African-violet, almond, ama- 
ranth, amaryllis, Amazon-lily, anemone, 
apple, apple-of-Peru, apricot, aster, bab- 
iana, barberry, basil, bean, beet, begonia, 
bellflower, blackberry, blackberry-1 i 1 y , 
bluegrass, bougainvillea, boysenberry, 
broccoli, Brussels sprouts, buttercup, but- 
terflyweed, cabbage, calceolaria, calendula, 
candytuft, canna, cantaloup, cape-cowslip, 
cape-marigold, caraway, carnation, carrot, 
cassaba, catnip, cauliflower, celeriac, cel- 
ery, chayote, cherry, chervil, chicory, 
China-aster, Chinese cabbage, Chinese hi- 
biscus, Chinese lanternplant, chrysanthe- 
mum, cineraria, citron, clematis, coleus, 
columbine, coriander, corn, cornflower 
aster, cosmos, cranesbill, crimson daisy, 
crinum, crocus, cucumber, currant, dahlia, 
damesrocket, daphne, datura, delphinium, 
dewberry, dill, eggplant, elm, emilia, en- 
dive, erysimum, euonymus, evening-prim- 
rose, false-garlic, fennel, fig, fleabane, 
flowering cherry, flowering raspberry, 
flowering tobacco, foxglove, freesia, fritil- 
laria, gaillardia, garden cress, garlic, ger- 
anium, gherkin, gladiolus, goldenchain, 
goldenglow, gooseberry, gourds, grape, 
groundcherry, ground-ivy, hackberry, 
heliopsis, heliotrope, hibiscus, hollyhock, 
honesty, honeydew melon, honeysuckle, 
horseradish, houndstongue, hyacinth, hy- 
acinth-bean, iris, ixia, Jerusalem-cherry, 
kale, kohlrabi, larkspur, lavatera, leek, 
lentil, lettuce, lilac, lily, lithospermum, 
lobelia, lupine, mallow, mangel, mangold, 
marigold, matrimony-vine, mertensia, 
mock-cucumber, monarda, monkshood, 
morning-glory, muskmelon, mustard, nar- 
cissus, nasturtium, nectarine, New Zealand 



spinach, nicotiana, nightshade, onion, 
orchids, oxeye daisy, pansy, parsley, pars- 
nip, pea, peach, peanut, pear, penstemon, 
peony, pepper, peppergrass, periwinkle, 
petunia, phacelia, phlox, pinks, pitto- 
sporum, plum, potato, primrose, pro- 
boscisflower, pumpkin, purple-coneflower, 
radish, rape, raspberry, rhubarb, rose, rud- 
beckia, rutabaga, salvia, sassafras, seakale, 
shallot, sida, sidalacea, skyrocket, snap- 
dragon, soapberry, spiderlily, spinach, 
squash, squill, star-of-Bethlehem, stock, 
stokesia, strawberry, streptanthera, sum- 
mer-hyacinth, sunflower, sweet alyssum, 
sweetpea, sweetpotato, sweet-william, Swiss 
chard, teasel, thimbleberry, tigerflower, 
tobacco, tomato, tritonia, tulip, turnip, 
verbena, vinca, violet, wallflower, wand- 
flower, watercress, watermelon, watsonia, 
wheatgrass, wisteria, and zinnia. 

Control: Use resistant varieties where 
adapted. Control insects, especially aphids, 
using malathion, nicotine sulfate, or lind- 
ane. Destroy infected garden plants when 
first found as they will not recover. Keep 
down weeds in and around the garden 
area which may harbor viruses. Use virus- 
free stock — certified or indexed if pos- 
sible. Destroy crop debris after harvest 
by burning or plowing under cleanly. Do 
not propagate from infected plants. 

(17) Spotted Wilt, Ringspot Symptoms vary 
with the particular virus-plant combi- 
nation. Leaves often show yellowish or 
dead concentric rings, oakleaf, zigzag, or 
watermark patterns, sometimes with green 
or yellow centers. Young leaves are usu- 
ally puckered and malformed. Plants are 
often stunted; yield is sharply reduced. 
Yet some plants apparently recover. Foli- 
age may be bronzed with dead spots de- 
veloping. Stems and petioles may show 
lengthwise dark streaks or rings. Stem tips 
often appear blighted, may collapse. The 
viruses are spread by thrips and possibly 
other insects. 

Plants Attacked: Almond, amaryllis, 
anemone, apricot, aster, bean, beet, be- 
gonia, blueberry, broccoli, Brussels 
sprouts, browallia, buttercup, butterfly- 
flower, cabbage, calceolaria, calendula, 
California-poppy, calla, candytuft, canta- 
loup, Canterbury-bells, carnation, cassaba, 
cauliflower, celeriac, celery, cherry, chicory, 
China-aster, Chinese lanternplant, chrys- 
anthemum, cineraria, columbine, corn, 



58 



GENERAL DISEASES 




HEALTHY 



Fig. 33. Spotted wilt. A. Tomato, B. Dahlia. Note the wide range of symptoms produced. 
On dahlia the viruses are sometimes called ringspot, yellow ringspot, and oakleaf dis- 
ease. 



cosmos, cucumber, dahlia, datura, del- 
phinium, eggplant, emilia, endive, erysi- 
mum, fleabane, flowering tobacco, fox- 
glove, fuchsia, gaillardia, garden cress, 
geranium, gilia, gladiolus, gloxinia, go- 
detia, gourds, groundcherry, hydrangea, 
iris, Jerusalem-cherry, kale, kohlrabi, let- 
tuce, lilac, lily, lobelia, lupine, lychnis, 
mallow, mignonette, muskmelon, mustard, 
narcissus, nasturtium, New Zealand spin- 
ach, nicotiana, okra, orchids, pansy, pars- 
nip, pea, peach, penstemon, peony, peper- 
omia, pepper, petunia, plum, poppy, 
potato, primrose, privet, pumpkin, radish, 
rape, rhubarb, salvia, satin-flower, scab- 
iosa, sea-lavender, spinach, squash, stock, 
strawflower, sunflower, sweet alyssum, 
sweetpea, sweet-william, Swiss chard, tidy- 
tips, tobacco, tomato, turnip, verbena, 
vinca, violet, wallflower, watermelon, yel- 
low ironweed, and zinnia. 
Control: Destroy infected plants when 
first seen. Keep down weeds in and 
around the garden area, e.g., bindweed, 



nettle, mallow, chickweed, galinsoga, etc. 
Control insects, especially thrips. Use 
DDT or methoxychlor and malathion. 
Plant disease-free stock. Destroy crop 
debris after harvest. 

(18) Yellows, Aster Yellows, Rosette, 
Dwarf, Stunt Symptoms variable depend- 
ing on the virus-plant combination and 
weather factors. Entire plants, or certain 
parts, are often more or less uniformly 
yellow (sometimes red or purple) , 
stunted, or dwarfed. May wilt and die 
prematurely. Leaves and shoots may be 
slender and stunted forming tight, up- 
right "rosettes." Fruit may ripen pre- 
maturely. Usually lacks flavor or may be 
"warty." Flowers may be greenish, 
dwarfed, aborted, or even absent. The 
viruses are spread primarily by leafhop- 
pers (or aphids for a few viruses) and 
by propagating infected stock which may 
appear normal. 

Plants Attacked: Allium, almond, alyssum, 
amaranthus, anagallis, anchusa, anemone, 



GENERAL DISEASES 



59 



anise, apricot, artichoke, avens, babys- 
breath, bachelors-button, basketflower, 
bayberry, bean, beet, begonia, bellflower, 
blackberry, black-salsify, blueberry, blue 
laceflower, broccoli, browallia, bur-mari- 
gold, buttercup, butterfly-flower, cabbage, 
calendula, California-poppy, camomile, 
canna, Canterbury-bells, cape-marigold, 
caraway, cardoon, carnation, carrot, cauli- 
flower, celeriac, celery, centaurea, cherry, 
chicory, China-aster, Chinese cabbage, 
chrysanthemum, cineraria, clarkia, clock- 
vine, cockscomb, cornflower, corn-mari- 
gold, cosmos, crimson daisy, cucumber, 
dahlia, daisies, delphinium, dewberry, 



dianthus, dill, eggplant, endive, English 
daisy, escarole, eupatorium, fennel, fire- 
wheel, flax, fleabane, forget-me-not, gail- 
lardia, garlic, geranium, gilia, gladiolus, 
globe-amaranth, globe artichoke, gloxinia, 
godetia, goldenglow, grape, groundsel, 
gypsophila, heronsbill, leek, lettuce, lily, 
lobelia, loganberry, love-lies-bleeding, 
mallow, mangel, mangold, marguerite, 
marigold, matricaria, mignonette, monkey- 
flower, mullein-pink, muskmelon, mus- 
tard, nasturtium, nectarine, New Zealand 
spinach, onion, oxeye daisy, painted- 
tongue, pansy, parsley, parsnip, pea, 
peach, peanut, petunia, phlox, pimpernel, 



Fig. 34. Yellows or stunt. A. Dahlia stunt, dwarf, or mosaic, B. Aster yellows on carrot, 
C. Peach yellows, D. Aster yellows on aster. 




>£»£. 



HEALTHY 



DISEASED 







HEALTHY 



DISEASED 



DISEASED 



HEALTHY 



60 



GENERAL DISEASES 



piqueria, plum, potato, primrose, prune, 
pumpkin, pyrethrum, radish, rape, rasp- 
berry, rudbeckia, rutabaga, salsify, salvia, 
sassafras, satin-flower, scabiosa, sea-laven- 
der, shallot, sneezeweed, speedwell, spin- 
ach, squash, statice, strawberry, straw- 
flower, summer-cypress, sunflower, Swan 
River daisy, sweet alyssum, sweet-william, 
Swiss chard, tickseed, toadflax, tomato, 
vegetable-marrow, vinca, wallflower, and 
zinnia. 

Control: Same as for Mosaic and Spotted 
Wilt. Control insects, especially leafhop- 
pers (and a few aphids) which transmit 
the viruses. Use DDT or methoxychlor 
and malathion at least weekly, when in- 
sects are present or expected. Asters, cer- 
tain other flowers, and lettuce are often 
grown under fine cheesecloth (22 threads 
per inch) or wire screening (18 threads 
per inch) to keep out insects. 
(19) Curly-Top, Western Yellow Blight 
Common and destructive in the western 
United States and other areas where light 
intensity and summer temperatures are 
high and the relative humidity is low. 
Symptoms vary with virus-plant combi- 
nation. Plants usually stunted or dwarfed 
with leaves mottled, bunched, curled 
downward, rolled, thickened, and yel- 
lowed. Flowers and buds may drop early. 
Plants Attacked: Alyssum, amaranthus, 
bean, beet, broccoli, buttercup, cabbage, 
campanula, cantaloup, carnation, carrot, 



cassaba, cauliflower, celeriac, celery, cher- 
vil, China-aster, Chinese cabbage, Chinese 
lanternplant, chrysanthemum, citron, 
cockscomb, collards, columbine, cori- 
ander, cornsalad, cosmos, cress, cucumber, 
delphinium, dill, eggplant, fennel, flower- 
ing flax, flowering tobacco, four-o'clock, 
foxglove, geranium, gherkin, globe-amar- 
anth, godetia, groundcherry, heliotrope, 
heronsbill, honeydew melon, horseradish, 
kochia, larkspur, lettuce, lobelia, mallow, 
mangel, marguerite, mignonette, mock- 
cucumber, morning-glory, muskmelon, 
mustard, nasturtium, New Zealand spin- 
ach, nicotiana, okra, oxalis, pansy, parsley, 
parsnip, pepper, peppergrass. petunia, 
phacelia, pinks, poppy, potato, pumpkin, 
pyrethrum, radish, rhubarb, rose-moss, 
rutabaga, salad chervil, salsify, scabiosa, 
Shasta daisy, spiderflower, spinach, squash, 
stock, strawflower, sweetpotato, sweet-wil- 
liam, Swiss chard, tickseed, tomato, turnip, 
vegetable-marrow, veronica, vinca, violet, 
watermelon, and zinnia. 
Control: Same as for Yellows. Plant as 
early as possible or at the time recom- 
mended for your area. 
(20) Leaf, Bud, Stem, and Leaf Gall 
Nematodes Symptoms variable with plant 
host. The nematodes live over winter in 
the soil or in infested leaves and stems. 
During the growing season the nematodes 
may swim up the stem in a film of water. 
Infestation only occurs when plants have 




HEALTHY 

DISEASED 





HEALTHY 



DISEASED 



B 




Fig. 35. Curly-top. A. Carnation, B. Strawflower. 



GENERAL DISEASES 



61 





B 



HEALTHY 




DISEASED 

Fig. 36. Leaf, stem, and leaf gall nematodes. A. Chrysanthemum foliar or leaf nema- 
tode, B. Strawberry dwarf or crimp. 



been wet as a result of rain, sprinkling, 
heavy dew, and fog. 

1. Begonia, chrysanthemum, ferns, lan- 
tana, orchids — Dark brown to black, 
angular, or wedge-shaped areas on 
the leaves. Often delimited by the 
leaf veins. Leaves may wither and 
die starting at the base of the plant. 

2. Strawberry — Leaves often stunted, 
narrow, twisted, crinkled, and cup- 
ped (spring and summer crimp or 
dwarf) . 

3. Bellf lower, sweet-william — Leaves 
very narrow, crinkled, wavy, often 
brittle. Stems may be swollen near 
the tops, or curved sideways. In- 
fested plants are stunted, fail to 
bloom, or may die prematurely. 

4. Lily — Leaves are bronzed, gnarled, 
blotched, and curled tightly down- 
ward {bunchy top) , later die back. 

See (38) Bulb Nematode. 
Plants Attacked: African-violet, anemone, 
aster, balsamroot, beet, begonia, bell- 



flower, bentgrass, bouvardia, butter-and- 
eggs, buttercup, butterfly-flower, calceo- 
laria, carrot, celery, chrysanthemum, clem- 
atis, coleus, coralbells, crassula, cyclamen, 
dahlia, daisy, delphinium, evening-prim- 
rose, ferns, four-o'clock, foxglove, garden 
cress, garlic, geranium, glory-of-the-snow, 
gloxinia, gooseberry, grape-hyacinth, 
groundcherry, ground-pink, groundsel, 
heuchera, hyacinth, hydrangea, lantana, 
leopardsbane, lily, loosestrife, lupine, mar- 
igold, monkeyflower, moonflower, narcis- 
sus, onion, orchids, oxalis, oxeye daisy, 
pansy, parsley, parsnip, peony, pepper- 
grass, phlox, pinks, piqueria, poppy, prim- 
rose, potato, privet, radish, rape, rhubarb, 
salsify, salvia, scabiosa, schizanthus, snow- 
drop, strawberry, sunflower, sweetpotato, 
sweet-william, teasel, toadflax, tomato, 
tulip, verbena, violet, wyethia, and zinnia. 
Control: Buy clean plants, certified and 
heat-treated if possible. Take tip cuttings 
from healthy plants. Collect and burn in- 
fested plants or plant parts as soon as 



62 



GENERAL DISEASES 



noticed. Burn tops at the end of the sea- 
son. Avoid overhead watering. Keep 
water off the foliage. Apply a dry mulch. 
Practice a 2-year rotation. Where practi- 
cal, apply malathion twice weekly until 
nematodes are controlled. Certain potted 
plants, such as African-violet, begonia, 
and ferns may be dipped in hot water 
to rid them of nematodes. 

B. Stem Diseases 

(21) Crown, Foot, Stem, Stalk, Collar, or 
Rhizome Rot; Stem Blight, Southern Blight, 
Damping-off Plants are generally first un- 
thrifty with leaves smaller and lighter 
green than normal. Leaves may later turn 
yellow or wilt, wither, and curl during 
hot, dry periods. Base of stems may be 
water-soaked and discolored and rotten. 
Leaves then wilt, turn yellow, wither, and 
eventually die. Roots may decay. Seedlings 
usually wilt and collapse (damping-off) . 
Stand may be poor. A cottony, or other 



type of mold, may grow over affected 
plant parts. Variously shaped, tan to 
black bodies (sclerotia) may be formed 
in this mold growth. Plants often wilt and 
gradually or suddenly die when the basal 
rot shuts off the supply of water and 
nutrients to the aboveground plant parts. 
See (2) Bacterial Spot, (6) Downy Mil- 
dew, (29) Bacterial Soft Rot, (32) Fruit 
Spot, and (34) Root Rot. 
Plants Attacked: Practically all plants. 
Control: Plant in a light, well-drained, 
well-prepared soil or in a sterile rooting 
medium (pages 437-44) , such as sand, soil, 
vermiculite, perlite, or sphagnum moss. 
Where possible, keep the soil on the dry 
side. Avoid overcrowding, overwatering, 
too deep planting, and overfertilizing 
(especially with nitrogen) . Water seed- 
lings at 5- to 7-day intervals with a solu- 
tion containing 1 to \i/ 2 tablespoons of 
ferbam, ziram, captan, thiram, or zineb 
per gallon of water. Use about i/ 2 pint 





HEALTHY 



DISEASED 



kms#&&>' ■■■• 



HEALTHY 



DISEASED 





Fig. 37. Crown or stem rot. A. Chrysanthemum crown and root rot, B. African-violet, 
C. Crown, rhizome, or bulb rot of iris, D. Blackleg of geranium. 



GENERAL DISEASES 



63 



per square foot of bed surface. Where 
possible, sterilize the soil with heat or 
chemicals before planting. Buy disease- 
free, crack-free seed of vegetables and 
flowers. Treat seed with captan, thiram, 
or chloranil before planting, as given 
under the plant involved and Table 13 in 
the Appendix. Practice as long a crop ro- 
tation as practical. Carefully collect and 
burn infected plants and several inches of 
surrounding soil. Soak flower bed soil in 
the infected areas with a 1:1,000 solution 
of mercuric chloride (see page 85 for 
precautions) , or apply Terraclor (PCNB) 
75 per cent and thiram, captan, or phal- 
tan (i/ 3 pound each per 100 square feet) 
to the soil surface before disease starts and 
mix into the top 5 to 6 inches of soil. 
Collect and burn all crop debris immed- 
iately after harvest, or plow under deeply 
and cleanly. Valuable plants may often be 
saved by taking tip cuttings or buds to 
start new plants. 

(22) Stem, Twig, Branch, or Trunk Canker; 
Dieback; Stem, Cane, or Limb Blight Both 
fungi and bacteria are responsible for pro- 
ducing cankers on the stems, twigs, limbs, 





Fig. 38. Stem canker and anthracnose. A. 

Raspberry anthracnose, B. Various rose 

cankers. 

and trunks. Cankers are usually definitely 
marked, shrunken, discolored areas 
(especially in the bark) which slow 
normal healing of wounds. Many cankers 
crack open, exposing the wood beneath. 
If the canker enlarges and girdles the 
stem, the parts above the diseased area 



usually wilt, wither, and die back from 
the tip. See also under (14) Seal), (15) 
Wilts, (23) Wood Rot, and (24) Fire 
Blight. 

Plants Attacked: Abutilon, acacia, alder, 
almond, amelanchier, American bladder- 
nut, amorpha, ampelopsis, apple, apricot, 
araucaria, arborvitae, arbutus, arrowwood, 
ash, asparagus, asparagus-fern, aspen, 
aster, aucuba, avocado, azalea, bald- 
cypress, barberry, bean, beech, beet, 
bignonia, birch, bittersweet, blackberry, 
black gum, black locust, bladder-senna, 
blueberry, Boston ivy, boxelder, boxwood, 
boysenberry, broccoli, broom, butterfly- 
bush, butternut, cabbage, cacti, caesal- 
pinia, calendula, California-laurel, calli- 
carpa, calycanthus, camellia, camphor-tree, 
carissa, carnation, carrot, cassia, catalpa, 
cauliflower, ceanothus, cedar, cherry, 
cherry-laurel, chestnut, chicory, China- 
aster, chinaberry, chinquapin, chokeberry, 
chrysanthemum, clarkia, clematis, colum- 
bine, coralberry, cornel, cosmos, coton- 
easter, cottonwood, crabapple, cucumber, 
currant, cypress, daphne, delphinium, 
dewberry, dogwood, Douglas-fir, eggplant, 
elder, elm, English ivy, euonymus, exa- 
cum, fennel, fig, filbert, fir, flowering al- 
mond, flowering cherry, flowering currant, 
flowering quince, flowering raspberry, for- 
sythia, foxglove, fuchsia, gardenia, gera- 
nium, gentian, goatsbeard, goldenchain, 
goldenlarch, goldenrain-tree, gooseberry, 
grape, grapefruit, hardhack, hardy orange, 
hawthorn, hazelnut, hemlock, Hercules- 
club, Hiba arborvitae, hibiscus, hickory, 
highbush cranberry, holly, hollyhock, 
holodiscus, honeydew melon, honeylocust, 
honeysuckle, hophornbeam, hornbeam, 
horsechestnut, India rubber tree, incense- 
cedar, inkberry, Japanese pagodatree, Jap- 
anese plum-yew, jasmine, jetbead, juni- 
per, kalanchoe, kale, kerria, larch, lemon, 
lilac, lily, lime, linden, locust, London 
plane, loquat, lupine, magnolia, mallow, 
maple, meconopsis, "mimosa" tree, monks- 
hood-vine, morning-glory, mountain-ash, 
mulberry, muskmelon, nectarine, oak, 
okra, oleander, onion, orange, osier, 
pachysandra, pagodatree, palms, paper- 
mulberry, parsnip, pawpaw, pea, peach, 
peanut, pear, pecan, pepper, persimmon, 
phlox, pine, pinks, planetree, plum, poin- 
ciana, poinsettia, poplar, potato, prairie- 
gentian, prickly-ash, privet, pumpkin, 
pyracantha, quince, radish, rape, rasp- 



64 



GENERAL DISEASES 



berry, redbay, redbud, redcedar, redwood, 
rhododendron, rhubarb, rose, rosemallow, 
Russian-olive, rutabaga, sassafras, senna, 
sequoia, serviceberry, silk-oak, silverberry, 
smoketree, snapdragon, snowberry, soap- 
berry, sophora, sorreltree, spicebush, spin- 
ach, spirea, spruce, squash, sumac, stock, 
sweet alyssum, sweetgale, sweetgum, sweet- 
pea, sweetpotato, sweet-william, sycamore, 
thimbleberry, tomato, tree-of-Heaven, 
tuliptree, tupelo, turnip, umbrella-pine, 
viburnum, vinca, Virginia-creeper, walnut, 
watermelon, weigela, white-cedar, willow, 
wisteria, wolfberry, woodwaxen, yellow- 
cedar, yellowwood, yew, and zinnia. 
Control: Carefully prune out and burn 
infected plant parts, cutting one to several 
inches behind the canker and including 
all discolored wood. On trees and shrubs, 
where practical, sterilize pruning shears 
between cuts by dipping or swabbing with 
70 per cent denatured alcohol. Follow the 
spray schedules for fruits listed in Table 
10 in the Appendix. Spraying with a 
multipurpose spray may be beneficial to 
certain flowers, shrubs, and vegetables. 
Treat seed of vegetables and flowers as in 
Table 13 of Appendix. Plant in sterilized 
soil and avoid overwatering. Treat bark 



and wood injuries of trees and shrubs 
promptly by covering with a tree wound 
dressing (page 25) . Keep plants grow- 
ing vigorously through fertilization, prun- 
ing, and watering during droughts. Avoid 
wounding plants. Plant resistant varieties 
where possible. 

(23) Wood, Butt, Wound, Heart, or Sap- 
wood Rot Certain fungi cause spongy or 
hard rots in both living and dead woody 
plants. Damage usually occurs slowly, 
often over a period of many years. Infec- 
tion occurs almost entirely through un- 
protected wounds such as pruning cuts, 
mowing bruises, breaks due to ice and 
windstorms, etc. Wood rots are often in- 
dicated by external, punky to woody, 
hoof- or shelf-shaped fungus structures 
(conks) , or by clusters of small toadstools 
at the base of the trunk, or at wounds. 
Affected wood may be discolored or 
stained. See also (34) Root Rot. 
Plants Attacked: Practically all woody 
plants. 

Control: Promptly treat bark and wood 
injuries with a tree wound dressing (page 
25) to prevent wood-rotting fungi from 
becoming established. If rot is evident, cut 
out cleanly all diseased wood and bark. 





i\ '#/ 



Fig. 39. Several types of fungus fruiting bodies (conks) which indicate wood rot 

is within. 




Fig. 40. Fire Blight. A and C. Apple, B. Fear. Note that in C infection has progressed 
down the shoot and is producing a canker in the branch. 



66 



GENERAL DISEASES 



Sterilize the cavity by painting with 
household bleach (diluted 1 to 5 with 
water) or a 1:1,000 solution of mercuric 
chloride (see page 85 for precautions) . 
Then cover with wound dressing. Keep 
plants growing vigorously by fertilization, 
pruning, and watering. 
(24) Fire Blight, Bacterial Shoot Blight, 
Bacterial Canker, Gummosis Blossoms, 
leaves, and fruit suddenly turn brown or 
black and shrivel as if scorched by fire, 
but cling to twigs. Twigs are shrunken 
and brown to black. The twig tips are 
often bent to form "shepherds' crooks." 
Rapidly growing shoots (e.g., water- 
sprouts and suckers) are especially sus- 
ceptible. The fire blight bacteria live-over 
in branch and trunk cankers. These 
cankers are slightly sunken, discolored 
areas with a sharp margin (or slight 
crack) separating healthy and diseased 
bark tissues. Fire blight is spread from 
overwintering cankers to blossoms, leaves, 
and young twigs by insects, splashing rain, 
wind, and pruning tools. See (2) Bacte- 
rial Leaf Spot and Blight. Blight is active 
from about the blossoming period until 
rapid shoot growth ceases. 
Plants Attacked: Almond, amelanchier, 
apple, apricot, avens, blackberry, cherry, 
chokeberry, cinquefoil, cotoneaster, crab- 
apple, flowering almond, flowering cherry, 
flowering quince, goatsbeard, hawthorn, 
holodiscus, jetbead, kerria, lilac, loquat, 
medlar, mountain-ash, ninebark, peach, 
pear, photinia, plum, pyracantha, quince, 
raspberry, rose, serviceberry, spirea, stran- 
vaesia, and strawberry. 
Control: Use resistant varieties of apple, 
crabapple, and pear or species of coton- 
easter and pyracantha. See under Apple. 
Avoid heavy fertilization (especially using 
nitrogen) , heavy pruning, and other prac- 
tices which stimulate excessive growth. 
Grow trees in sod in well-drained soil. Cut 
out infected twigs and small limbs during 
the dormant season, pruning at least 4 
inches back from the canker margin. Cut 
out cankers on large limbs or trunk and 
disinfect the wound before coating with 
a tree wound dressing to which Elgetol 
or Krenite has been added as a disinfec- 
tant (page 25) . Disinfect pruning tools 
between cuts by dipping them in 70 per 
cent denatured alcohol or a 1:1,000 solu- 
tion of mercuric chloride (page 85) . For 
additional information read USDA Leaf- 



let No. 187, Blight of Pears, Apples, and 
Quinces. 

If practical, spray with streptomycin or 
zineb at 3- to 5-day intervals beginning at 
very early bloom and continuing through 
the blossoming period. These sprays are 
expensive and will not control the serious 
twig blight stage which follows. Follow 
the manufacturer's directions. 
(25) Black Knot Rough, black swellings 
on twigs and branches. Knots are covered 




Fig. 41. Black Knot. A. Cherry, B. Plum. 

with an olive-green, velvety surface in late 
spring. If left undisturbed, black knot 
may stunt and kill trees. 
Plants Attacked: Apricot, cherry, Mayday- 
tree, peach, and plum. 
Control: Cut out and burn infected twigs 
and branches during the dormant season. 
Make pruning cuts 3 to 4 inches back of 
the knot. Knots on large limbs should be 
removed by surgery (page 24) . The cuts 
should go back into healthy wood. Cover 
pruning wounds with a tree wound dress- 
ing (page 25) . Destroy nearby wild plums 
and cherries and any worthless fruit trees. 
Follow the spray program as outlined in 
Table 10 in the Appendix. 

(26) Rust Powdery, yellow-orange galls or 
swellings on twigs, limbs, and trunk, or 
bean-shaped galls on junipers which be- 
come orange and gelatinous in spring 
rains. See (8) Rust. 

(27) Smut Sooty, powdery masses on stems 
and branches. See (11) Smut. 

(28) Leafy Gall, Fasciation, Witches'-broom 
Symptoms variable. Dwarfed, thick, 
aborted shoots with distorted leaves de- 



GENERAL DISEASES 67 





Fig. 42. Leafy gall or fasciation. A. Sweetpea, B. Geraniur 



velop near the soil line. Main stem is 
stunted. Few flowers are produced. See 
(30) Crown Gall. 

Plants Attacked: Babysbreath, butterfly- 
flower, carnation, chrysanthemum, dahlia, 
geranium, hollyhock, nasturtium, nico- 
tiana, petunia, phlox, piqueria, pyreth- 
rum, Shasta daisy, strawberry, and sweet- 
pea. 

Control: Where practical, dig up and 
burn infected plants. Plant disease-free 
seed or dip 1 minute in alcohol, then 
soak 20 minutes in a 1:1,000 solution of 
mercuric chloride (see page 85 for pre- 




cautions) . Rinse and wash well in run- 
ning water before drying and dusting the 
seed with thiram or captan. Sterilize soil 
in flower beds or use fresh soil (pages 437- 
44). Maintain good cultural practices. 
Plant disease-free stock. Practice a 3-year 
rotation. 

(29) Bacterial Soft Rot, Bacterial Stem Rot, 
Collar Rot Rapid, mushy, slimy, or 
"cheesy" rot, usually with a putrid odor. 
Roots, stems, fleshy tubers, bulbs, buds, 
leaves, and fruit become soft, watery, and 
pulpy. Foliage wilts, shrivels, and may 
collapse when lower stem or underground 




Fig. 43. Bacterial soft rot. A. Soft rot and blackleg of potato, B. Iris. 



68 



GENERAL DISEASES 



parts rot. Infections occur through 
wounds. Rot is most destructive in warm, 
moist weather. See also under (21) Crown 
Rot, (32) Fruit Spot, and (36) Bulb 
Rot. 

Plants Attacked: Apple, artichoke, aspar- 
agus, bean, beet, broccoli, Brussels sprouts, 
cabbage, cacti, caladium, calla, canna, 
cantaloup, carrot, cassaba, cauliflower, 
celeriac, celery, chicory, Chinese cabbage, 
chrysanthemum, citron, collards, corn, 
cucumber, cyclamen, cypress, dahlia, dash- 
een, delphinium, dieffenbachia, eggplant, 
elephants-ear, endive, escarole, European 
cranberry-bush, fennel, ferns, finocchio, 
fittonia, garlic, geranium, gladiolus, 
gourds, horseradish, hyacinth, iris, Jeru- 
salem-cherry, kale, kohlrabi, leek, lettuce, 
lily, mangel, muskmelon, mustard, night- 
shade, okra, onion, orchids, pansy, parsley, 
parsnip, pea, pear, pepper, poinsettia, 
potato, pumpkin, radish, rape, redwood, 
rhubarb, rutabaga, salsify, sansevieria, 
shallot, spinach, squash, strawberry, sweet- 
potato, tomato, tuberose, tulip, turnip, 
violet, and watermelon. 
Control: Avoid planting in poorly 
drained, unfertile soil. Treat soil before 
planting using aldrin, dieldrin, chlordane, 
etc., to control soil insects. Carefully dig 
up and burn infected plants. When rot 
starts in flower beds, disinfect soil by 
drenching with a 1:1,000 solution of mer- 
curic chloride (see page 85 for precau- 
tions) . Repeat treatment 10 days later. 
Spray to control foliage-feeding insects 
using DDT or methoxychlor plus mala- 
thion. Control foliage blights, fruit rots, 
and other diseases. Practice a long crop 
rotation. Avoid wounding plants when 
cultivating, digging, etc. Store only dry, 
sound, vegetables and fruits in a dry, well- 
ventilated room at the recommended 
temperature and humidity. The storage 
area should first be swept clean. Then 
spray all surfaces from ceiling to floor 
with a formaldehyde solution (1 pint of 
commercial 37 per cent formalin in 10 
gallons of water) or scrub down with a 
copper sulfate solution (1 pound in 5 
gallons of water) before storing fruits, 
vegetables, roots, etc. Leafy vegetables 
should be precooled to 45° F. or below 
and then placed in cold storage as soon 
after harvest as possible. 

For calla and iris: Cut out rotted por- 
tion in bulb, corm, or rhizome. Then dry 
thoroughly for a day or two. Before plant- 



ing soak in a 1:1,000 solution of mercuric 
chloride. 

(30) Crown Gall, Cane Gall, Hairy Root, 
Bacterial Root Gall Rough-surfaced, hard 
or soft and spongy, swollen tumors or 
galls, up to several inches in diameter. 
May be flesh-colored, greenish or dark. 
Galls are usually found at or near the 
soil line, at the graft or bud union, or on 
the roots and stems. Small, fibrous roots 
are sometimes profuse, may resemble 
"witches'-brooms." These occur at the 
base of the trunk, crown, or on the 
larger roots. As the disease progresses, 
plants often become stunted and sickly. 
May eventually die. The crown gall bac- 
teria enter through wounds. Easily con- 
fused with callus overgrowths formed at 
wounds or graft unions — which are per- 
fectly normal. Corn, onions, asparagus, 
grasses, and cereals are immune. 
Plants Attacked: Achillea, almond, apple, 
apricot, araucaria, arbutus, artemisia, ash, 
asparagus-fern, aster, azalea, babysbreath, 
balsam, bean, beet, begonia, bittersweet, 
blackberry, blueberry, boysenberry, cab- 
bage, cacti, caesalpinia, calendula, caly- 
canthus, camellia, cape-jasmine, carnation, 
carrot, castorbean, catalpa, chamaecyparis, 
cherry, chrysanthemum, cinquefoil, clem- 
atis, clockvine, cotoneaster, cottonwood, 
crabapple, cucumber, cypress, dahlia, 
daisy, delphinium, dewberry, dogwood, 
Douglas-fir, euonymus, fig, filbert, flower- 
ing quince, forsythia, foxglove, geranium, 
grape, grapefruit, hazelnut, hibiscus, hick- 
ory, hollyhock, honeylocust, honeysuckle, 
horseradish, incense-cedar, India rubber 
tree, jasmine, Jerusalem-artichoke, Jeru- 
salem-cherry, juniper, kalanchoe, lemon, 
lettuce, lilac, lippia, loquat, lupine, mal- 
low, mangel, mangold, maple, marguerite, 
mountain-ash, mulberry, muskmelon, nec- 
tarine, New Jersey-tea, nicotiana, oak, 
orange, parsnip, peach, pear, pea-tree, 
pecan, peony, persimmon, phlox, plum, 
poinciana, poinsettia, poplar, potato, 
privet, quince, radish, raspberry, redcedar, 
rhubarb, rose, rosemallow, Russian-olive, 
rutabaga, Shasta daisy, snapdragon, snow- 
berry, spirea, Sprenger asparagus, straw- 
berry-tree, sumac, sunflower, sweetpea, 
tomato, turnip, viburnum, walnut, 
weigela, white-cedar, willow, witch-hazel, 
wisteria, wormwood, yew, and yucca. 
Control: Carefully dig up and burn in- 
fected plants, especially woody ones. Re- 
move as many of the infected roots as 







Fig. 44. Crown gall. A. Apple, B. Rose, C. Crown and cane gall of raspberry, D. Peach. 



70 



GENERAL DISEASES 



possible. Practice at least a 3-year rotation 
or avoid replanting in the same location 
for that period or longer. Reject plants 
showing suspicious bumps near the crown, 
former soil line, or graft union. Budding 
is preferable to grafting. Where suspi- 
cious, dip grafting knives in 70 per cent 
denatured alcohol between cuts. Avoid 
wounding plants when cultivating, etc. 
Disinfestation of infested soil using steam 
or chemicals (e.g., Vapam, V.P.M. Soil 
Fumigant, D-D, EDB, chloropicrin, etc.) 
is seldom complete unless the soil is in 
ccnfined containers (pages 437-44) . Main- 
tain the soil as acid as practical (below 
pH 5.5) for vegetables. Control insects by 
sprays of malathion and methoxychlor or 
DDT. Some nurserymen dip woody plant- 
ing stock immediately after digging in a 
Terramycin solution (about 400 parts per 
million) for 15 minutes, followed by air 
drying. Others dip planting stock in a 
1:1,000 solution of mercuric chloride for 
1 to 10 minutes. If galls are severe on 
larger trees, call in a reputable arborist. 
He will probably excavate, chisel off the 
outer gall tissue, and paint the gall and 
its margins with a mixture of Elgetol (1 
part) and methanol (4 or 5 parts) . The 
damaged areas should then be painted 
with a tree wound dressing (page 25) . 

C. Flower and Fruit Diseases 
(31) Flower or Blossom Blight, Ray or In- 
florescence Blight Flowers spotted, often 
wither or rot, causing fruit not to set, or 
young fruit may rot and drop early. 
Flowers and young fruit may be covered 
with dense mold growth during and fol- 
lowing moist weather. See also under (5) 
Botrytis Blight, (6) Downy Mildew, (7) 
Powdery Mildew, (9) White Rust, (11) 
Smut, (16) Mosaic and Flower Breaking, 
(18) Yellows, (19) Curly-top, (24) Fire 
Blight, and (38) Bulb Nematode. 
Plants Attacked: African-violet, almond, 
amaranth, amelanchier, anemone, apple, 
apricot, aucuba, avocado, azalea, black- 
berry, blueberry, calla, camellia, castor- 
bean, cherry, Chinese hibiscus, cherry- 
laurel, chokeberry, Christmas-rose, chrys- 
anthemum, cornflower aster, crabapple, 
cucumber, cyclamen, dahlia, delphinium, 
dewberry, dogwood, flowering almond, 
flowering cherry, flowering quince, for- 
sythia, foxglove, geranium, gladiolus, haw- 



thorn, hibiscus, hyacinth, hydrangea, iris, 
Japanese quince, jasmine, lilac, lily, lo- 
quat, magnolia, Maltese cross, maple, 
marigold, mistflower, mockorange, morn- 
ing-glory, mountain-ash, mountain-laurel, 
narcissus, nectarine, okra, orchids, palms, 
pea, peach, pear, peony, pepper, petunia, 
plum, pumpkin, quince, raspberry, rhodo- 
dendron, rose, rose-of-Sharon, snapdragon, 
snowberry, squash, strawberry, stock, stok- 
esia, sumac, sweetpea, thimbleberry, 
tomato, tuberose, tulip, verbena, vi- 
burnum, yucca, and zinnia. 
Control: Treat flower and vegetable seed 
before planting as given in Table 13 in 
the Appendix. Follow spray or dust sched- 
ules for vegetables and fruit. Spray others 
with captan, thiram, zineb, maneb, or a 
copper-containing fungicide. Apply a 
light, misty spray of zineb at 3- to 5-day 
intervals during bloom. Rotate garden 
plantings. If practical, carefully remove 
affected and fading flowers and young 
fruit when first noticed. Place in a paper 
sack and burn. Space plants. Avoid over- 
head sprinkling. Plant in well-drained 
soil. 

(32) Fruit Spot, Speck, Rot, or Blotch; Seed, 
Berry, or Tuber Rot; Storage Rot Fruit, 
tuber, berry, etc., shows one or more spots. 
Spots often enlarge and run together. 
Whole fruit may later rot and shrivel. 
Frequently starts at the blossom or stem- 
end or on the underside of fruit when 
resting on damp soil. Bacterial Soft Rot 
may follow causing a mushy or watery, 
foul-smelling decay. See also under (6) 
Downy Mildew, (10) Leaf Curl, (11) 
Smut, (12) Sooty Mold, (14) Scab, (16) 
Mosaic, (21) Crown Rot, (29) Bacterial 
Soft Rot, (31) Flower Blight, and (36) 
Bulb Rot. 

Plants Attacked: Almond, amelanchier, 
apple, apricot, artichoke, avocado, bar- 
berry, bean, beet, blackberry, blueberry, 
boysenberry, butternut, cabbage, canta- 
loup, carrot, cassaba, cauliflower, celery, 
chayote, cherry, chestnut, China-aster, 
chokeberry, citron, coralberry, crabapple, 
cucumber, currant, dahlia, dasheen, dew- 
berry, eggplant, endive, feijoa, fig, flower- 
ing almond, flowering quince, fragrant 
glad, gaultheria, gladiolus, gooseberry, 
gourds, grape, grapefruit, guava, hardy 
orange, hawthorn, hazelnut, hickory, 
honeydew melon, huckleberry, kumquat, 




Fig. 45. Flower blight. A. Tulip fire, B. Gladiolus, C. Botrytis blight on geranium, D. 

Head blight of chrysanthemum. 




Fig. 46. Fruit rots. A. Bitter rot of apple, B. Tomato anthracnose, C. Black rot of 
sweetpotato, D. Brown rot of plum. 



GENERAL DISEASES 



73 



lemon, lettuce, lime, loquat, mock-cucum- 
ber, mountain-ash, mulberry, muskmelon, 
nectarine, okra, olive, onion, orange, 
palms, parsnip, pea, peach, peanut, pear, 
pea-tree, pecan, pepper, persimmon, 
plum, pomegranate, potato, pumpkin, 
pyracantha, quince, radish, raspberry, rol- 
linia, rutabaga, snowberry, squash, straw- 
berry, sweetpotato, tomato, turnip, wal- 
nut, watermelon, yam, and yautia. 
Control: Mulch vegetables to keep fruit 
off soil. Follow spray or dust programs for 
vegetables and fruit. Control insects which 
transmit disease organisms and provide 
entrance wounds. Use malathion plus 
methoxychlor or malathion plus DDT. 
Promptly collect and burn (or eat) spot- 
ted and rotting fruit. Guard against 
wounding fruit and vegetables from har- 
vest through the storage period. Store 
only sound, blemish-free fruit and vege- 
tables at the recommended storage tem- 
perature and humidity. Check with your 
extension horticulturist. Treat seed of 
vegetables and flowers as given under the 
plant involved and in Table 13 in the 
Appendix. Plant only high-quality seed. 
Resistant varieties are available for some 
plants. 

(33) Smut Flower parts or seed may break 
open to release a black, powdery mass. See 
(11) Smut. 

D. Root and Bulb (Corm) Diseases 

(34) Root Rot, "Decline," Cutting Rot 

Symptoms variable. Plants may gradually 
lose vigor, becoming sickly or yellowed 
and stunted. Plants tend to wilt or die 
back and do not respond normally to 
water and fertilization. Young plants wilt 
and collapse. Affected plants are more 
subject to wind damage — may blow over 
or lodge. Root rot is often difficult to diag- 
nose because the trouble is hidden from 
view. Roots decay. May be covered with 
mold growth, and be brown, black, white, 
or gray in color. Decay may be water- 
soaked, mushy, spongy, or firm. Easily 
confused with wilts, bacterial soft rot, 
crown rots, root-feeding insects, or nema- 
todes. Nematodes often provide wounds 
by which root-rotting fungi and bacteria 
enter. Usually most serious on annual 
plants in cold, wet, poorly drained soils. 
See under (15) Wilts, (21) Crown Rot, 
(35) Clubroot, (36) Bulb Rot, and (37) 
Root-knot. 



In the southwestern states (Oklahoma 
and Texas to southeastern Utah, Nevada, 
and California) a widespread soil fun- 
gus (Phymatotrichum) causes a disease 
known as Texas or Cotton Root Rot. 
Over 1,700 kinds of plants including fruit 
and shade trees, shrubs, flowers, and vege- 
tables are attacked from midsummer on. 
Phymatotrichum often kills plants in 
more or less circular patches, up to an 
acre or more in diameter. A firm brown 
rot of the lower stem and roots occurs. 
Affected roots may be covered with a 
dirty-yellow weft of mold and brown or 
black bodies (sclerotia) . The fungus is 
only found in alkaline soils (pH 7.3 and 
above) . If you live in the Texas Root 
Rot area, contact your state or extension 
plant pathologist for a listing of resistant 
plants and other control measures which 
are effective against this disease. 
Plants Attacked: Practically all plants. 
Control: Plant in a well-drained, well- 
prepared soil high in organic matter 
(page 16) . Practice a systematic crop 
rotation. Burn tops of annual plants af- 
ter harvest. Dig up and burn affected 
garden plants. Sterilize soil for seedbeds 
and house plants (see pages 437-44 in the 
Appendix) . Start seed of very susceptible 
plants in a sterile or uninfested medium 
(e.g., vermiculite, sifted sphagnum moss, 
perlite or soil) . Treat seed before plant- 
ing. See Table 13 in the Appendix. Avoid 
overcrowding and overwatering in the 
seedbed. Keep perennial plants growing 
vigorously through proper fertilization, 
watering, cultivating, and pruning. 
Avoid close and deep cultivations. Prac- 
tice balanced soil fertility. Keep down 
weeds. If possible, do not replant trees 
in the same location where previous 
woody plants have died from Root Rot. 
Applying a soil drench of Fumazone, Ne- 
magon, or VC-13 Nemacide around living 
plants may be beneficial if root-feeding 
nematodes are present in large numbers. 
(35) Clubroot Attacks crucifers. Plants 
may not head, but remain stunted and 
sickly. Often plants wilt on hot, dry days 
and partially recover at night. Outer 
leaves may turn yellow and drop. The 
roots form a mass of small to large, dis- 
torted, club-shaped swellings. They later 
rot from secondary organisms. 
Plants Attacked: Alyssum, broccoli, Brus- 
sels sprouts, cabbage, candytuft, Chinese 




Fig. 47. Root rots. A. Black root rot of strawberry, B. Armillaria root and wood rot, a 
common disease of woody plants, C. Root and corm rot of gladiolus, D. Root and stem 

rot of pea. 



GENERAL DISEASES 



75 



cabbage, cauliflower, collards, dames- 
rocket, erysimum, garden cress, honesty, 
horseradish, kale, kohlrabi, mustard, pep- 
pergrass, radish, rockcress, rutabaga, sea- 
kale, stock, sweet alyssum, turnip, and 
wallflower. 

Control: If practical, apply enough hy- 
drated lime to the soil about 6 weeks be- 
fore planting to reach a pH of 7.2 or 
higher. Where possible, either avoid or 
drain wet soils. Plant disease-free seed- 
lings in sterilized soil (pages 437—44), 
water seedbed with a 1:2,000 solution (1 
ounce in 15 gallons of water) of mercuric 
chloride (see page 85 for precautions) or 
work Terraclor (PCNB) into the top 4 
to 6 inches of soil about 2 weeks before 





Fig. 48. Clubroot. A. Cabbage, B. Mus- 
tard. 



planting. Apply broadcast or as a band. 
Follow the manufacturer's directions. Add 
Terraclor to the transplanting water (see 
under Cabbage) . Varieties differ in re- 
sistance. Rutabagas, most turnips, pepper- 
grass, horseradish, kale, and garden cress 
are usually very resistant. Practice a long 
rotation, keeping out all cruciferous 
weeds (e.g., charlock, wild radish, wild 
mustards, pennycress, shepherds-purse, 
yellow-rocket, or wintercress) . Collect and 
burn crop debris after harvest. 
(36) Bulb (Corm) or Rhizome Rot Shoots 
fail to emerge or are sickly with yellow 
leaves which die back progressively from 
the tips. Roots often discolored and de- 



cayed. Usually associated with nematodes, 
bulb mites, and insects. Decay often starts 
at bulb base (root or basal plate, bottom 
of stem) and progresses upward and out- 
ward. Spots may also develop on the 
side or neck of the bulb. There may be 
little external evidence of rot although 
bulbs may be lightweight and soft or 
punky. Rot usually progresses in stor- 
age, especially if the temperature and 
moisture are not controlled. See (29) 
Bacterial Soft Rot, (32) Fruit Rot, (34) 
Root Rot, and (38) Bulb Nematode. 
Plants Attacked: Acidanthera, allium, 
amaryllis, chives, colchicum, crocus, free- 
sia, garlic, gladiolus, glory-of-the-snow, 
grape-hyacinth, hyacinth, iris, ixia, leek, 
lily, lily-of-the-valley, lycoris, narcissus, 
onion, shallot, snowdrop, snowflake, 
squill, tigerflower, tritonia, tuberose, tu- 
lip, and zephyranthes. 
Control: Plant or store disease-free bulbs 
(and corms) free of rot spots. Cure bulbs 
thoroughly and as rapidly as possible af- 
ter digging. Sort carefully at digging time, 
before storage, and again just before 
planting. Treat bulbs or corms before 
planting. See under the plant involved 
and Table 13 in the Appendix. Rotate 
crops or plant in sterilized, well-drained 
soil (pages 437-44) . 

(37) Root-knot, Root Gall, Cyst Nematode 
Nematode-infested plants usually lack 
vigor, are often stunted and yellowish. 
May resemble soil deficiency symptoms, 
crown rot, root rot, etc. Severely infected 
plants may wilt in dry weather but re- 
cover at night for a time, then may 
wither and die. Small to large swellings, 
galls or knots, develop on the roots which 
are more or less round, or long and ir- 
regular — cannot be broken off, like the 
nodules on legume roots. Roots may be- 
come "beaded," swollen, or greatly dis- 
torted. Widespread and damaging in 
many southern soils, especially light, well- 
aerated ones. Both yield and quality are 
reduced. Primarily an indoor problem 
in the most northern states, although 
there is one species of root-knot which is 
found mostly in northern states. Root- 
knot is distributed in infested nursery 
stock, in root crops, and soil transported 
on shoes, sacks, crates, tools, or equip- 
ment. Root-knot and cyst nematodes may 
increase the severity of certain wilt dis- 
eases and root rots. 




BASAL ROT 



SOFT 
MEALY ROT 



SCALE TIP ROT 




k NECK ROT 




6 



BASAL OR 
WHITE ROT 



BROWN 
SCALE ROT 




Fig. 49. Bulb rots. A. Narcissus, B. Onion, C. Lily, D. Tulip. 



GENERAL DISEASES 



77 



Plants Attacked: Practically all except 
certain grasses, grains, and weeds. 
Control: Where practical, sterilize (fumi- 
gate) the soil or rooting medium using 
heat or chemicals (e.g., D-D, Dor- 
lone, EDB, chloropicrin, Telone, Vapam, 
V.P.M., or Mylone; see page 89 and 
pages 437-44 in the Appendix) . The soil 
temperature at treating time should gen- 
erally be 60° to 65° F. or above. The soil 
is commonly fumigated in the fall after 
harvest while the soil is still warm. Nema- 
gon, Fumazone, and VC-13 Nemacide 
may be used around many types of in- 
fested living plants. Follow the manufac- 
turer's directions carefully. Plant disease- 
free nursery stock and certified transplants 
of cabbage, tomato, and certain other 
plants. See (34) Root Rot. 



(38) Bulb Nematode, Ring Disease, Onion 
Bloat Symptoms variable. Usually plants 
are stunted with the foliage twisted, 
crinkled, and yellow. Petioles are often 
swollen and cracked. The main roots may 
be discolored and develop furrows and 
cracks. 

1. Hyacinth — Yellow to brown flecks or 
blotches on the leaves which become 
twisted, short, and split. Flower stalks 
are stunted and flowers are malformed. 
Bulb scales become thickened and turn 
brown. Cut bulbs are the same as for 
Narcissus. 

2. Narcissus — Small, yellowish, blisterlike 
swellings on the leaves. Badly infested 
bulbs produce only a few twisted and 
bent leaves or none at all. Infested 
bulb scales are brown. When infested 




Fig. 50. Root-knot. A. Carrot, B. Watermelon, C. Dahlia, D. Tomato. 



78 



GENERAL DISEASES 





6 



HEALTHY 



i« c FASEO 




CROSS SECTION 
Fig. 51. Bulb nematodes. A. Onion bloat, B. Ring Disease of hyacinth. 



bulbs are cut through, one or more 

dark rings are evident. 
3. Onion — Seedlings dwarfed, twisted, 

and abnormally white. Young bulbs 

are swollen and misshapen (bloated) , 

and become soft. 
Nematodes are spread by tools, running 
water, animals, infested soil, and planting 
infested bulbs. 

Plants Attacked: Chives, collomia, dahlia, 
galtonia, garlic, glory-of-the-snow, grape- 
hyacinth, hyacinth, iris, lycoris, narcissus, 
onion, parsley, shallot, squill, sweetpotato, 
tigerflower, and tulip. 
Control: Destroy infested plants. Plant 
disease-free bulbs or seeds in sterilized or 



clean soil (see pages 437-44 in the Ap- 
pendix) . Avoid heavy, poorly drained 
soil. Soak fully dormant narcissus and 
hyacinth bulbs in hot water and formal- 
dehyde. See Daffodil and Tulip. Collect 
and burn tops, infested bulbs, and other 
crop debris in the fall. Practice a 3-year 
or longer rotation with noninfected crops. 
Keep down weeds. 

E. Parasitic Flowering Plants 

(39) Mistletoes There are two general 
types: American or true mistletoes and 
dwarf mistletoes. 

American or True Usually leafy, evergreen 
tufts of shoots with yellow to dark green, 



GENERAL DISEASES 



79 



leathery leaves. White, yellow, or pink- 
ish to red berries are produced. The sticky 
seeds are easily spread by birds and 
animals. Infections commonly occur on 
tree branches after birds wipe the seeds 
from their beaks. The leafy masses of 
American or true mistletoes may be up to 
3 feet in diameter. They are most con- 
spicuous after the leaves drop in the 
fall. 

Found as far north as Oregon, where 
winters are not severe. Only relatively 
young branches are attacked. Tree 
branches beyond the mistletoe may be 
stunted, even die. Once established, the 
mistletoe may live as long as the tree it 
feeds upon. This is the mistletoe used 
for Christmas greens. 

Dwarf Perennial, scaly-leaved, simple or 
branched shoots on conifers. The stems 
vary from yellow to brown to olive-green 
in color. Berries are olive-green to dark 
blue. The sticky seeds are explosively shot 
out of the fruit. This type of mistletoe is 



often less than an inch in diameter, but 
may be up to 8 inches. Dwarf mistletoes 
may seriously stunt or deform the growth 
of evergreen trees, especially seedlings and 
young trees. Conspicuous witches'-brooms 
are formed in the crown or spindle-shaped 
swellings (later cankers) in the trunk. 
Branches or even entire trees may be 
killed. Most common in the western states 
in forested areas. 

Plants Attacked: Acacia, alder, apple, ash, 
beech, birch, black gum, black locust, 
buckeye, camphor-tree, chinaberry, 
cherry, cherry-laurel, cypress, dogwood, 
Douglas-fir, elaeagnus, elm, fir, forestiera, 
frangipani, hackberry, hawthorn, hem- 
lock, Hercules-club, hickory, honeylocust, 
horsechestnut, incense-cedar, juniper, 
larch, linden, locust, manzanita, maple, 
oak, Osage-orange, osmanthus, paper-mul- 
berry, parkinsonia, pear, pecan, persim- 
mon, pine, planetree, plum, poplar, 
prickly-ash, redcedar, sassafras, smoketree, 
soapberry, sophora, spicebush, spruce, 



Fig. 52. Mistletoe. A. American or true mistletoe on apple, B. Dwarf mistletoe 



on pine. 




80 



GENERAL DISEASES 



sugarberry, sweetgum, sycamore, tama- 
rack, trumpetvine, tupelo, walnut, and 
willow. 

Control: Cut off young infected branches 
a foot or more beyond any evidence of 
the mistletoe. For older branches cut out 
the bark and wood a foot or more away 
from each infection. Apply disinfectant 
to the wound surface and paint with tree 
wound dressing (page 25) . If an ever- 
green trunk is infected with dwarf mistle- 
toe, the tree should be cut down when- 
ever practical. 

(40) Dodder, Strangle Weed, Love Vine, 
Gold Thread Orange to yellow, "leafless," 
slender, twining vines which are parasitic 
on a wide range of garden plants. Occurs 
in tangled patches which take on a yel- 
lowish-orange color as the dodder chokes 
out the vigor of garden plantings. 
Control: Plant clean vegetable and flower 
seed free of the rough, flat-sided, gray to 
reddish-brown, dodder seed. When dod- 
der is found on garden plants, carefully 
remove and burn all infested plants be- 
fore the dodder forms seeds. Locate 
patches early, before the plant spreads. 
When breaking new soil suspected of be- 
ing dodder-infested, fumigate it before 
planting by using a soil fumigant (see 
next section and pages 439-44 in the Ap- 
pendix) . Areas known to be heavily in- 
fested with dodder seed should be planted 
to resistant plants, e.g., grass, corn or 
small grains for at least two years in suc- 
cession. Where this cannot be done, the 
use of a soil fumigant is advisable. A 




Fig. 53. Dodder on aster. 



glove, moistened with dilute 2,4-D spray 
and dried, may be used to stroke dodder 
plants strangling a valuable plant. If any 
dodder survives after three days, repeat 
the treatment. Check with your county 
agent, extension weed specialist, or hor- 
ticulturist for details. 



SECTION 3 



"What Can I Do About It?" 



MEASURES 

Plant adapted varieties and 

types of plants 82 

Buy disease-free planting stock 82 

Treat the seed 

Control damping-off .... 

Plant in a well-prepared and 
well-drained seedbed . . . 

Follow a recommended crop 
rotation 

Pasteurization of infested soil 

and compost 83 

Control weeds 83 

Control insects, mites, and 

rodents 83 

Avoid deep and close cultiva- 
tions 

Sanitary measures are impor- 
tant 

Changing a cropping practice 

Store only sound, dry fruits and 

Destroy or remove alternate 
hosts of rust diseases . . . 



84 



Apply protective fungicid 


es 




84 


MATERIALS 


What Is a Fungicide? .... 84 


Protective fungicides 






84 


Eradicant fungicides 






84 


Chemotherapeutants 






84 


Modern Fungicides . . 






84 


Other Useful Fungicides 






85 


Karalhane .... 






85 


Mercuric chloride 






85 


Terraclor 






85 


Fixed copper fungicide. 






88 


Bordeaux mixture 






88 


Sulfur products . . 






88 


Phaltan 






88 


Antibiotics .... 






88 


A. Streptomycin 






88 


B. Acti-dione . . 






89 



Phenyl mercury materials . 89 
Broad-spectrum lawn fungi- 
cides 89 

Chemical Soil Treatments (fumi- 
gants and temporary soil 

sterilants) 89 

Safety Precautions When Han- 
dling Pesticides 89 

Measuring Apparatus .... 90 

When Spraying or Dusting . . 90 

Multipurpose Sprays and Dusts 91 
For vegetables, fruit, flowers, 

trees, and shrubs ... 91 

"Shot-gun" Soil Drench ... 92 

To Spray or To Dust? .... 92 

EQUIPMENT 

Sprayers and Dusters .... 92 

A. Sprayers 92 

Household sprayers . . 93 

Compressed air sprayers 93 

Knapsack sprayers . . 95 
Slide pump or trombone 

sprayers 95 

Wheelbarrow, cart, and 

barrel sprayers ... 95 

Garden hose sprayers . 95 

Small power sprayers 98 

Maintenance of Sprayers . .100 

B. Dusters 100 

Plunger type dusters . . 1 00 
Small bellows, crank, or 

rotary-fan dusters . .100 

Knapsack dusters ... 1 00 

Small power dusters . .104 

* * * 

Maintenance of Dusters ... 104 
Spreaders, Stickers, and Wetting 

Agents 104 

Fungicide Manufacturers and 
Distributors Plus Leading 
Spraying and Dusting Manu- 
facturers 104 



[81 ] 



82 



KEEPING THE DISEASE IN CHECK 



Once a plant problem has been diag- 
nosed as a disease (see also Section 4) , the 
next question is, "What can I do about 
it?" When a disease has progressed suffi- 
ciently to be easily recognized, it is often 
too late to start a spray or dust control 
program. Prevention and protection are 
usually the answer. Start before the dis- 
ease appears. Tree surgery, however, is 
useful as a curative measure in the control 
of many cankers, blights, and decays of 
woody plants. 

Successful disease control should start 
with the purchase of the best seed or 
planting stock available and should con- 
tinue in the seedbed, through the season 
in the field, and even after harvest until 
the product is completely disposed of. 
There is much more to disease control 
than just dusting and spraying. 

A number of different practices may be 
needed to help keep diseases in check. 
These include: 

Plant adapted varieties and types of 
plants recommended by your state agri- 
cultural experiment station, cooperative 
extension service, and reputable seedsmen 
or nurserymen as being adapted to your 
area. Such varieties should include those 
having resistance to common diseases, plus 
possessing other desirable horticultural 
qualities. Unfortunately, resistant types 
are often less valuable because of some 
undesirable quality (e.g., poor foliage, in- 
ferior flowers or fruit, low yield) . There 
are different degrees of resistance varying 
from tolerance or partial resistance to 
complete immunity. 

Progress with control by resistant varie- 
ties is hindered because parasitic organ- 
isms mutate or otherwise produce new 
races which attack varieties which were 
formerly resistant or immune. Certain 
fungi, bacteria, and viruses are known to 
have many different physiologic races or 
strains. 

Buy disease-free planting stock from a 
reputable nursery whose stock is carefully 
checked at least once each season by ex- 
perienced nursery inspectors. This in- 
sures you of comparative freedom from 
damaging insects, mites, and diseases. If 
available, buy certified disease-free seed, 
propagating material, or plants. Disease- 
free seed is often grown in arid parts of 
the western United States, under irriga- 
tion, where many diseases are unknown 



(e.g., black rot and blackleg of cabbage, 
bean anthracnose and pea blights) . Use 
seed, bulbs, corms, tubers, cuttings, or 
other plant parts, only from healthy 
plants. 

Treat the seed of most flowers and vege- 
tables against seed rot and damping-off by 
dusting the seed lightly with thiram, cap- 
tan, or chloranil (see Table 13 in the 
Appendix) before planting. Follow the 
manufacturer's directions. Seed can be 
treated in small packets or in larger 
quantities using Mason jars. See page 427 
in the Appendix. Seed treatment is good 
insurance for increased stands and bigger 
yields, especially if the soil is cold and 
wet after planting. 

Seeds, bulbs, corms, roots, and rhizomes 
may be disinfected by hot water or mer- 
cury which kills organisms (bacteria, 
fungi, nematodes) on the surface as well 
as within. See Table 13 in the Appendix. 
Care should be taken with small seeds 
which are more readily injured by dis- 
infectants than larger seeds. 

Control damping-off. Occasionally captan, 
ferbam, zineb, phaltan, thiram, Pano- 
drench, or Semesan, 1 to 2 tablespoons in 
a gallon of water, applied at the rate of 
i/ 2 to 1 pint per square foot, checks the 
advance of damping-off, root and crown 
rots. Terraclor is also useful for certain 
soil-borne fungi, especially those that pro- 
duce sclerotia. Before soaking the in- 
fested area with the fungicide, the 
diseased plants and about 6 inches of 
surrounding soil should be removed. The 
manufacturer's directions should be care- 
fully followed. Do not use mercury-con- 
taining fungicides (e.g., Semesan, Pano- 
drench) in confined areas or on such 
susceptible plants as pansy, petunia, vio- 
let, rose, and snapdragon. 

For a good multipurpose "shot-gun" 
soil drench, see page 92. 
Plant in a well-prepared and well-drained 
seedbed, at times most suitable for your 
area. Follow the planting instructions and 
cultural practices published by your state 
agricultural experiment station and co- 
operative extension service and those 
given in nursery and seed catalogs. These 
instructions should include information 
on seedbed preparation, depth and rate 
of planting, spacing for efficiency and 
care of seedlings. 



KEEPING THE DISEASE IN CHECK 



83 



Follow a recommended crop rotation 
that excludes the same or closely related 
crops in the same garden area for 3 or 
4 years or more. Most disease-causing 
organisms persist in the soil, or in decay- 
ing crop debris, from one year to the 
next. A proper rotation "starves out" 
many of these organisms. The fungi caus- 
ing clubroot of cabbage and fusarium 
wilts, for example, can live almost indefi- 
nitely in the soil without their favorite 
host plants being present. Some disease- 
causing organisms can remain alive 
through a compost pile or passage in the 
digestive tract of farm animals. 

Pasteurization (usually called steriliza- 
tion) of infested soil and compost is often 
an important control practice. See pages 
437-44 in the Appendix regarding when 
and how to disinfest soil using heat or 
chemicals (fumigants). All plant-parasitic 
organisms are killed by heating the soil 
to a temperature of 180° F. for 30 min- 
utes. 

Control weeds (by cultural or chemical 
means) , especially perennials and winter 
annuals. Weeds are important reservoirs 
of insects, viruses (e.g., especially mosaics 
and aster yellows) and other disease-pro- 
ducing agents. Viruses can easily be car- 
ried to nearby garden plants by insects 
(e.g., leafhoppers, aphids, thrips, grass- 
hoppers, and whiteflies) and mites. Weeds 
also decrease air circulation and slow 
normal drying of the foliage following 
wet periods. This leads to more severe in- 
jury from leaf spots, blights, and mildews. 
The serious drain of plant nutrients and 
water from the soil by weeds is well- 
known to all gardeners. Check with your 
county agent or extension weed special- 
ist regarding the latest weed control 
recommendations. 

Control insects, mites, and rodents. Many 
diseases are spread largely or entirely by 
insects and mites. Most foliage-feeding 
insects and mites can now be controlled 
by using a multipurpose spray or dust 
containing malathion plus methoxychlor, 
DDT, lindane, Sevin, rotenone, or re- 
lated materials. Excellent insecticides for 
controlling underground-feeding insects 
contain aldrin, dieldrin, or chlordane. If 
insect, mite, and rodent feeding could be 
prevented, losses from fruit rots, wood 
decays, root and crown rots, certain wilts 



and foliage diseases could be materially 
decreased. Check with your county agent 
or extension entomologist regarding the 
latest insect and rodent control recom- 
mendations. 

Avoid deep and close cultivations. Culti- 
vator wounds weaken plants and provide 
easy entrance for fungi and bacteria-pro- 
ducing root and crown rots, certain wilts, 
root rots, and crown gall. 

Sanitary measures are as important in 
keeping plant diseases in check as they 
are for animal and human diseases. Col- 
lect and burn infected plants or plant 
parts as they become infected. A disease 
may start in one or several plants and 
then spread throughout a garden when 
conditions (moisture, right temperature) 
are favorable. Destroy (rogue) the first 
infected plants or plant parts as soon as 
found. This is very important with cer- 
tain virus diseases where entire plants 
should be destroyed. Burn tops after 
harvest is over or plow under such debris 
cleanly. Sanitary measures are equally 
important in controlling insect and mite 
pests. Avoid transferring bacteria, fungi, 
mites, and insect eggs on hands, clothing, 
or tools. Tools may be disinfected by 
dipping in 70 per cent denatured alco- 
hol, 5 per cent formaldehyde, household 
bleach, or a 1:1,000 solution of mercuric 
chloride (page 85) . Hands should be 
scrubbed with soap and hot water before 
handling healthy plants. Work among 
plants only when they are dry. 

Sanitary measures are often the only 
ones needed in the home garden. But it 
helps if you can convince your neighbors 
to do likewise! Pruning of infected twigs, 
branches, and shoots helps to control 
many diseases. But prune with discretion. 
Excessive pruning may stimulate excess 
shoot growth which is often more sus- 
ceptible to reinfection. Prune at least 
several inches below any sign of infection. 

Changing a cropping practice is often a 
good method of disease control. Staking 
tomato vines, instead of letting them lie 
on the ground, reduces losses from fruit 
rots. Pruning to open up trees and shrubs 
lets in sun, increases air circulation, and 
hence reduces the chance of foliage dis- 
eases getting a foothold. Shallow planting 
often means a better stand of seedlings 
under cold, wet conditions. Aeration of 



84 



WHAT IS A FUNGICIDE? 



the soil, application of a suitable fertil- 
izer, planting to escape migrations of leaf- 
hoppers, aphids, or other pests, and 
watering during drought periods are 
other means of escaping injury from cer- 
tain diseases. 

Destroy or remove alternate hosts of rust 
diseases. See (8) Rust under General Dis- 
eases. Which type of plant is destroyed 
will depend on such factors as the number 
and value of the plants involved. Many 
such plants can now be protected against 
rusts by the proper and timely appli- 
cation of fungicides. 

Store only sound, dry fruits, and vege- 
tables free of cuts, bruises, rot, insect or 
rodent injuries. Requisites of good stor- 
age are the proper temperature, aeration, 
humidity, (and moisture content, where 
applicable) plus cleanliness (page 172) . 
If in doubt concerning the recommended 
storage conditions for your garden pro- 
duce, check with your county agent or ex- 
tension horticulturist. The USDA Farm- 
ers' Bulletin No. 1939, Home Storage of 
Vegetables and Fruits, covers this subject 
in detail. For additional information on 
the most favorable temperature and ap- 
proximate length of the storage period 
for cut flowers, rhizomes, tubers, roots, 
bulbs, corms, and nursery stock, see a book 
such as the USDA Handbook No. 66, 
Commercial Storage of Fruits, Vegetables, 
Florist, and Nursery Stocks. 
Apply protective fungicides. This means 
applying the right chemicals in the right 
way at the right time and in the right con- 
centration. If this is done, there will be 
no danger of damaging tender plants or 
poisonous pesticides remaining on ripen- 
ing fruits and vegetables. 

It usually pays to follow a regular pre- 
ventive schedule. Applications should 
generally be made every 3 to 7 days in 
wet weather and at 10- to 14-day intervals 
if the weather is dry. If rains of an inch 
or more wash the fungicide away, re- 
apply. Insecticides should be applied on 
a planned, protective schedule every 7 
to 10 days, before large numbers of in- 
sects appear and damage occurs. For cer- 
tain insects closer spacing of sprays is 
needed. 

WHAT IS A FUNGICIDE? 

A fungicide is any chemical which pro- 
tects plants against disease-producing 



fungi that land by chance on the plant, 
as spores or mycelium. 

Fungicides can be conveniently di- 
vided into three groups, according to 
their action. 

Protective fungicides are applied as foli- 
age sprays or dusts and as seed or soil 
treatments to keep disease-causing fungi 
from entering plants. These materials 
will provide protection, but will not (I) 
kill fungi established within a growing 
plant or seed (Exceptions are the pow- 
dery mildews which are superficial and 
largely on the surface of plants. These 
mildews can be killed by surface dusts or 
sprays, after infection has occurred, with- 
out injury to the host plants.) , (2) pro- 
tect against disease organisms entering 
through the roots such as root rots, wilts, 
and clubroot, (3) control bacterial dis- 
eases — since most fungicides are poor 
bactericides. (4) protect against viruses, 
which are frequently injected into plants 
by insects, and (5) control nematodes. 

Most fungicides in use today (e.g., cap- 
tan, zineb, maneb, ferbam. thiram. copper- 
or sulfur-containing) are protective in 
nature. Foliage sprays or dusts should be 
applied before wet periods when the 
great majority of infections occur. 
Eradicant fungicides are applied as foli- 
age sprays, seed treatments or soil drenches 
to kill or check disease-causing fungi af- 
ter they have penetrated into plants and 
become established. Examples are phenyl 
mercury materials used by commercial 
apple growers to "burn out" apple scab 
infections, and the mercury-containing 
chemicals used on certain types of seed, 
bulbs, tubers, and rhizomes, to kill or- 
ganisms under the seed coat or within 
propagative plant parts. These fungicides 
have limited uses and are often dangerous 
to use on green foliage. 
Che mother a peut ants are chemicals ab- 
sorbed and distributed within the plant 
to control certain diseases. Very few 
chemicals now available work in this 
way, but chemotherapy is currently a 
very promising field of research. 

MODERN FUNGICIDES 

In the past few years a great many new 
fungicides have been introduced. These 
chemicals are rapidly replacing such old 
standbys as bordeaux mixture, other cop- 
per-containing materials, lime-sulfur and 



USEFUL FUNGICIDES 



85 



wettable or paste sulfur fungicides. Many 
of these older materials were messy to 
handle, corrosive to spray equipment, 
caused injury to plants and reduced both 
the quality and quantity of the crops 
they were designed to protect. Unfor- 
tunately, many garden supply stores, hard- 
ware stores, and drugstores do not stock 
modern fungicides. If you can't get some 
of the chemicals mentioned in this book 
or those recommended by your state co- 
operative extension service and agricul- 
tural experiment station, check with your 
county extension office or the list of 
names and addresses of leading fungicide 
manufacturers and distributors at the end 
of this section. If you can't get a pesticide 
you want locally you can always write di- 
rectly to the chemical manufacturer or 
distributor. 

The chemical names (called active in- 
gredients) of the new fungicides, printed 
on many package labels, are difficult to 
remember or pronounce. Fungicides are 
marketed under a bewildering assortment 
of trade names. To relieve confusion, a 
set of common names has been officially 
adopted and is being increasingly used 
on package labels in place of the more 
complicated chemical names. Table 1 
summarizes the common names, active in- 
gredients, trade names, major distribu- 
tors, and principal uses of the most com- 
mon modern fungicides. This listing is 
necessarily incomplete as there are over 
50,000 pesticides now registered by the 
Pure Food and Drug Administration in 
Washington, D.C. 

Where specific trade names are men- 
tioned in this book, it is to be understood 
they are not mentioned to the exclusion 
of other similar and competitive products. 
They are simply representative of the 
most generally available products in the 
United States. 

The most useful modern fungicides for 
the home gardener are captan, zineb, 
maneb, Karathane, Terraclor (PCNB) , 
and mercuric chloride. 

OTHER USEFUL FUNGICIDES 

Karathane contains dinitro phenyl croton- 
ate as the active ingredient. It is specific 
for the control of powdery mildews. Sold 
as Karathane-WD or Karathane L 
(Rohm & Haas) . Karathane has replaced 
sulfur in many multipurpose sprays and 
dusts. Compatible with practically all 



fungicides, insecticides, and miticides in 
these combination mixtures (page 91) . 
Do not use in hot weather (above 85° F.) . 
Apply when the foliage will dry rapidly. 
Used normally at the rate of i/ 2 to 2/ 5 tea- 
spoonful in a gallon of water. 

Mercuric chloride is also known as cor- 
rosive sublimate and bichloride of mer- 
cury. Used as a general disinfectant, soil 
drench, and dip treatment. Controls rots 
of gladiolus, calla, canna, and iris besides 
killing disease-causing organisms carried 
inside pepper, cucumber, melons, cab- 
bage, and other seed. The dipping time 
in mercuric chloride varies from 5 
minutes to 2 hours or longer, depending 
on the plant part treated. 

Mercuric chloride is a caustic, deadly 
poison and should be handled with cau- 
tion. It is usually sold by pharmacists as 
a white powder or in the form of tablets. 
Commonly prepared to make a 1 in 1,000 
solution by dissolving 1 ounce in 714 gal- 
lons of water, or one 7.3 grain tablet in 
a pint of water. Handle only in non- 
metallic containers such as wood, glass, 
enamel, or earthenware. Dissolve the chem- 
ical in a small amount of hot water and 
add to the rest of the water. Seeds, bulbs, 
and corms should be washed in clear, 
running water for 5 to 10 minutes after 
treating. Dry, then plant. See "Seed 
Treatment Methods and Materials" in the 
Appendix. 

Mercuric chloride and mercurous chlor- 
ide are combined in several useful lawn 
fungicides — Calo-clor, Calocure (Mal- 
linckrodt), Fungchex, and Woodridge 
Mixture "21." 

Terraclor contains PCNB (pentachlo- 
ronitrobenzene) . Is a long-lasting soil fun- 
gicide. Sold as a 75 per cent wettable 
powder, a 25 per cent emulsifiable con- 
centrate, or 10, 20, and 40 per cent dusts 
by the Olin Mathieson Corp. and the 
Stauffer Chemical Co. Controls various 
soil-borne root, stem, and crown rots of 
flowers, vegetables, and ornamentals, club- 
root of cabbage, potato scab and scurf, 
pink rot of celery, and damping-off of 
many plants. See Table 14 in the Appen- 
dix. We will see more of this chemical 
and other soil fungicides in the future. 
Often mixed with captan (Terracap and 
Orthocide Soil Treater "X") , ferbam, 
thiram, or phaltan, and applied as a dust 
or spray in the seedbed to control root 



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88 



USEFUL FUNGICIDES 



and stem rots, damping-off, and other 
diseases. 

Fixed copper fungicides are represented 
by a large group of trade names (e.g., 
Copper A Compound, Cuprocide, Basic 
Copper Fungicide, Farmrite M-53 Fixed 
Copper, Basi-Cop, Tri-Basic Copper Sul- 
phate, Coposil, Spray Cop, C-O-C-S, 
Microgel, Tricop, Ortho-K, Tennessee 
"26" Copper Fungicide, Ortho Copper 
Fungicide "53," Copper 53, Corona 53, 
Micro Nu-Cop, Copper Hydro, and many 
others) . Similar in usage to bordeaux 
mixture (sprays, dusts, soil drenches) , 
except fixed coppers often do not require 
mixing with lime, and, thus, do less dam- 
age to plants in cool, moist weather. 
Fixed coppers are also easier to handle 
and use. Copper-containing materials are 
still recommended to control various 
blights and leaf spots of vegetables, 
flowers, trees, and shrubs. Materials to be 
used as sprays usually contain from 53 to 
55 per cent metallic copper; dusts from 
5 to 11 per cent. 

Bordeaux mixture has largely been re- 
placed by new fungicides which do not 
''burn" leaves or "russet" fruit. Bordeaux 
is a mixture in water of copper sulfate 
(Milestone or blue vitriol) and spray 
lime. The formula is written in figures 
(e.g., 4-4-50) in which the first is copper 
sulfate in pounds, the second number is 
spray lime in pounds, and the third figure 
is water in gallons. 

For preparing small amounts of 4-4-50 
bordeaux mixture, dissolve 2 ounces of 
copper sulfate crystals in a gallon of 
water. Then dissolve 2 ounces of hydrated 
spray lime in 2 gallons of water. Add the 
copper sulfate solution to the lime water. 
Strain the mixture into the sprayer 
through several layers of cheesecloth and 
use immediately. This makes 3 gallons of 
4-4-50 bordeaux mixture. 

Various dry products, ready to mix 
with water, are available (e.g., Acme Bor- 
deaux Mixture, Bor-dox, Copper Hydro 
Bordo, and Ortho Bordo Mixture) but 
are generally inferior to homemade bor- 
deaux. Bordeaux is still used to control 
certain fungus leaf spots, blights, anthrac- 
nose, and as a general disinfectant for 
storage cellars, work surfaces, and other 
areas. Bordeaux paint is used as a tree 
wound dressing (page 25) . 
Sulfur products are available as wettable 



powders, pastes, liquids, and dusts under 
a variety of trade names. Twenty-five to 97 
per cent wettable or colloidal sulfur 
makes a fine suspension in water. For 
most effective disease control use wettable 
sulfurs with an average particle size of 
not more than 5 to 7 microns. Sulfur 
dusts should be fine enough to pass 
through a 300 or 325 mesh screen. Sulfur 
is used primarily to control powdery mil- 
dews on many plants, brown rot of stone 
fruits, certain rusts, leaf blights, and fruit 
rots. May cause injury in hot, dry 
weather especially to sulfur-sensitive 
plants like viburnum, raspberry, grape, 
and blueberry. Sulfur is being rapidly re- 
placed by newer fungicides. 

Lime-sulfur is effective against both 
fungi and certain insect and mite pests. 
It is most useful, when properly used, as 
a dormant or delayed dormant spray for 
trees, shrubs, and fruits to control blight 
or anthracnose, powdery mildew, apple 
scab, mites, and scale insects. Use liquid 
lime-sulfur at the rate of one pint of con- 
centrated lime-sulfur in 9 or 16 pints of 
water. Lime-sulfur is now considered too 
toxic to use for summer sprays. Keep it 
away from white paint unless you want 
the paint blackened! 

Phaltan — A new fungicide containing N- 
trichloromethylthiophthalimide. A close 
relative of captan. Sold as Ortho Rose 
Garden Fungicide and Ortho Phaltan 50 
Wettable (California S p r a y-Chemical 
Corp.) , as Phaltan 50 Wettable and 
Phaltan 75-W (Stauffer) , and Niagara 
Phaltan 50 Wettable (Niagara) . Excel- 
lent for roses and other plants. Also con- 
trols many powdery mildews. Expect to 
see phaltan in more multipurpose mix- 
tures in the future, especially for roses. 
Antibiotics — Recently antibiotics have 
been widely used to control plant diseases. 
Antibiotics may be absorbed through 
plant surfaces and be distributed within 
the plant to check or eradicate an infec- 
tion, plus protecting against other diseases 
becoming established. The future of these 
materials in the therapeutic control of 
certain, hard-to-control diseases is promis- 
ing. We can look forward to even more 
useful antibiotics in the future. Two of 
the most widely available are: 

A. Streptomycin — An antibacterial 
antibiotic sold commercially for plant use 
as Agri-mycin (Charles Pfizer) , Phytomy- 



SAFETY IN HANDLING PESTICIDES 



89 



cin (Squibb, Olin Mathieson) , Strepto- 
mycin Spray (Calif. Spray) , Streptomycin 
Antibiotic Spray (Miller) , Stauffer Strep- 
tomycin (Stauffer) , and Agristrep (Nia- 
gara) . Agri-mycin 500 (Charles Pfizer) is 
a mixture of streptomycin, copper, and 
terramycin. Agri-mycin 100 (Charles 
Pfizer and Chipman Chemical Co.) con- 
tains streptomycin and terramycin in com- 
bination. 

Streptomycin formulations are used to 
control the blossom blight stage of fire 
blight [ see (24) Fire Blight under Gen- 
eral Diseases], bacterial spot of pepper 
and tomato, bacterial wilts, blights, and 
rots of various trees and ornamentals, and 
blackleg of potato. 

B. Acti-dione — An antifungal antibio- 
tic sold by the Upjohn Co. Effective 
against such diseases as powdery mildew, 
cherry leaf spot, certain rusts and several 
lawn diseases. Acti-dione is used at such 
amazingly low concentrations as 1 part in 
1 million parts of water! Do not overdose 
with this chemical. Various formulations 
(e.g., Acti-dione BR, PM, RZ, ferrated, 
Actidione-captan, and Acti-dione-thiram) 
are sold for different purposes. Actispray 
(Upjohn and Niagara) is in a convenient 
tablet form which dissolves in water. 

Other new antifungal and antibacterial 
antibiotics will undoubtedly be widely 
available in the future. 
Phenyl (organic) mercury materials are 
useful in controlling a number of lawn 
diseases, certain leaf blights and spots of 
trees and shrubs, bulb rots, and a few 
fruit diseases (e.g., apple and peach 
scab) . These materials act both as pro- 
tective and eradicant fungicides. Sold as 
liquids: PMAS (Cleary) , Puratized Agri- 
cultural Spray, Puratized Apple Spray 
(Niagara) , Tag Fungicide or Crabgrass 
Killer and Turf Fungicide (Calif. Spray) , 
Coromerc Liquid (Pittsburgh Plate 
Glass) , Panogen Turf Spray or Pano- 
drench (Morton) , Phenyl Mercury Lac- 
tate and 10% Phenyl Mercury Acetate 
(Eastern States) ; and as powders: Phix 
(Chemley) and Coromerc (Pittsburgh 
Plate Glass) . Usually contain phenyl- 
mercury acetate (PMA) , phenylmercury 
chloride (PMC) , phenylmercury lactate 
(PML) , phenylmercury nitrate (PMN) , 
or phenylmercury monoethanol ammon- 
ium acetate. 
Broad-spectrum lawn fungicides — Several 



products are now available which control 
a wide range of lawn diseases. Some of 
these include Kromad (Mallinckrodt) , 
Formula Z (Vaughan Seed Co.) , Tersan 
OM (Du Pont) , Ortho Lawn and Turf 
Fungicide (Calif. Spray) , and Thimer 
(Cleary) . Zineb also controls a number of 
lawn diseases. 

CHEMICAL SOIL TREATMENTS 

Fumigants and temporary soil sterilants 
are chemicals which generally break down 
in the soil to release a toxic gas which 
kills bacteria, nematodes, weed seeds, in- 
sects, and other animal life in the soil. 
Some are also effective fungicides. Certain 
fumigants move through the soil slowly. 
Other fast-acting ones must be confined 
with a tarp or other covering. 

Many home gardens in the southern 
half of the United States are fumigated 
each year to control root-knot nematodes 
and other soil pests. See page 440 in the 
Appendix. 

Such common fumigants as EDB (ethyl- 
ene dibromide) , D-D (dichloropropene- 
dichloropropane) , Vapam or V.P.M. Soil 
Fumigant, and chloropicrin must be ap- 
plied two weeks or more before planting 
to prevent serious plant injury. Apply 
when the soil moisture is relatively high 
and the soil temperature is at least 60° to 
65° F., 4 inches deep. The soil around cer- 
tain actively growing ornamentals and turf 
may be treated with the relatively safe 
Nemagon (Shell) and Fumazone (Dow) . 
Other useful fumigants include Vapam 
(Stauffer), V.P.M. Soil Fumigant (Du 
Pont) , allyl alcohol, and Mylone (Union 
Carbide) . 

Use these materials strictly according 
to the manufacturer's directions. Observe 
all safety precautions. For a full discussion 
on Soil Treatment Methods and Materials 
see pages 437-44 in the Appendix. 

SAFETY PRECAUTIONS WHEN 

HANDLING PESTICIDES 

There is no pesticide (any chemical 
which kills pests) mentioned in this book 
which cannot be used with perfect safety 
if you follow the necessary precautions. 
In fact the chemicals were carefully 
chosen not only because of their general 
effectiveness but also for their relative 
safety to humans, animals, and plants. 



90 



MEASURING APPARATUS 



For an excellent discussion on how 
pesticides are safety-tested, plus the story 
of how agricultural chemicals are used 
to protect our food, property, and health, 
read a book such as Open Door to Plenty, 
published by the National Agricultural 
Chemicals Association, 1145 19th St. 
N.W., Washington 6, D.C. 

Laws governing the manufacture and 
distribution of pesticides require that the 
labels of dangerous chemicals contain: 

(1) the familiar skull and crossbones 
insignia, 

(2) the word "poison" in red letters, 
and 

(3) a statement of antidote. 

Such words as "Caution," "Warning," 
and "Danger" on a pesticide label indi- 
cate that the material is dangerous if 
misused. 

Read and understand the entire package 
label before purchasing. The information 
is printed for your protection. Read the 
instructions again before using. Fungi- 
cides, like other pesticides, should be used 
according to package directions, on the 
crops specified, in the amounts specified, 
and at the times specified. Observe other 
precautions listed, especially safe han- 
dling and frequency of application. 

Store chemicals in a locked, orderly-kept 
cabinet, outside the home, closed to ir- 
responsible adults, children, and pets. 
Running water should be handy to flush 
away any spilled chemicals. Promptly de- 
stroy old pesticide containers. 

Never use or store unlabeled chemicals, 
or those not in their original containers. 
Keep the pesticide container tightly closed 
except when preparing the mix. 

Never breathe dusts, mists, or vapors of 
pesticides. Avoid spilling on shoes or 
other clothing. Immediately flush with 
water any body area contacted, and re- 
move contaminated clothing and shoes. 

Wear full protective clothing where called 
for, when applying pesticides. This may 
include rolled down trouser legs and 
sleeves, turned up collar and a washable 
cap. Do not eat or smoke while using 
pesticides. 

Wash hands and face thoroughly before 
eating or smoking. Bathe promptly after 
spraying and change to fresh clothing. 
Launder clothing before reusing. 



Cover bird baths, pet dishes, and fish 
pools while spraying or dusting. 
Use wettable powder formulations or pre- 
pared dusts when combining insecticides 
and fungicides. Do not mix emulsion con- 
centrates with wettable powders. Check 
the pesticide compatibility chart (page 
446) in the Appendix before mixing 
chemicals together. 

Do not apply any spray when the 
temperature is 85° F. or above. 

Do not apply dormant oil sprays if the 
temperature is 40° F. or below or when 
the temperature is likely to drop below 
this figure during the next 24 hours. 

Do not contaminate your sprayer with 
weedkillers, especially those of the hor- 
mone type such as 2,4-D, 2,4,5-T, or 
MCP. It's better to get a second sprayer 
and paint "WEED KILLERS ONLY!" in 
red on the sides. 

Keep the sprayer or duster in good re- 
pair by following a regular maintenance 
program (pages 100, 104) . 

MEASURING APPARATUS 

For help in measuring out small to 
large amounts of liquids or powders (or 
conversion from one to the other) see 
pages 420—22 in the Appendix. 

To avoid guesswork and possible plant 
injury in mixing pesticides, the following 
equipment, where applicable, is sug- 
gested: 

1. For measuring wettable powders or 
liquids get a set of standard household 
measuring spoons. 

2. A letter balance is useful for weighing 
small amounts up to about 4 ounces. 

3. A spring balance for weighing up to 
4 pounds is something that many 
home gardeners will need. A larger 
scale weighing up to 25 pounds may 
be needed if large areas need spraying. 

4. If using liquids, assemble a set of 
standard containers (14 pint, i/ 2 pint, 
1 pint, 1 quart, 1 gallon, and 5 gal- 
lons) . 

Do not use this equipment in the kitch- 
en or for other household purposes. Keep 
it locked up with your pesticides. 

WHEN SPRAYING OR DUSTING 

For good disease and insect control it 
is important that all parts of the plant 
be uniformly coated. When spraying, be 
sure to spray from the top of the plant 



MULTIPURPOSE SPRAYS AND DUSTS 



91 



down, from the bottom up and the in- 
side out. Remember that many fungi and 
bacteria penetrate only the underleaf 
surface. Apply a fine, misty spray which 
wets the foliage evenly. Keep the spray 
stream moving. Wet all surfaces until 
drops start to fall (run off) . 

One quart of spray mix should cover 
a 50-foot row of most flowers and vege- 
tables when plants are young, and 20 to 
25 feet when full grown. 

Most sprays will be more effective if a 
wetting agent or spreader-sticker (see 
page 104) is added to the spray solution. 
Most household detergents and soaps are 
satisfactory. Add a sufficient amount 
(usually 14 to 1 teaspoonful per gallon 
of spray) so that the spray solution will 
spread out on the leaf surfaces and not 
run off as large drops. Good coverage is 
essential and a spreader will help. A 
spreader-sticker is essential on glossy, 
hard-to-wet leaves. 

The cone-type nozzle is generally pre- 
ferred when spraying garden plants. The 
fan-type nozzle is principally used for 
applying insecticides on building surfaces 
and to protect outdoor living areas 
against mosquitoes and flies. The fan or 
flat spray nozzle is preferred for applying 
weed sprays. 

If dusting, apply a thin dust film to 
all aboveground plant surfaces. Adjust 
the nozzles to insure puffing the dust up 
and through the plant. Apply dusts when 
plants are dry or nearly so and the air is 
calm. Early morning or evening is often 
best. 

One ounce of dust usually covers a 
50-foot row early in the season while 2 to 
3 ounces are required later. 

Always accurately measure the amounts 
of fungicide or insecticide spray materials 
you plan to use. The amounts which are 
recommended have been carefully calcu- 
lated to provide the correct amount. That 
extra spoonful you may add is only 



wasted — and may cause injury! Always 
measure, never guess. 

The measures given throughout this 
book are in LEVEL spoonfuls and cup- 
fuls. 

For additional information on spraying 
fruits, see pages 423—26 in the Appendix. 

MULTIPURPOSE SPRAYS AND DUSTS 

Multipurpose (one-package) sprays or 
dusts control a wide range of pests. They 
are easy and generally safe to use and 
have encouraged more home gardeners to 
keep their plants as pest-free as possible. 
Multipurpose sprays and dusts have largely 
eliminated the necessity of stocking a 
large assortment of garden medicines. 
Many chemical companies and nurseries 
now have these mixes designed especially 
for use on tomatoes, potatoes, roses, 
flowers, gladiolus, vegetables, and fruits. 
Most mixes can be used on a wide variety 
of plants. 

Found below are several safe and effec- 
tive mixtures, now recommended by a 
number of states. But be sure to read the 
fine printing on the label before you buy. 
Methoxychlor, DDT, malathion, and 
rotenone are added to kill insects and 
mites. 

Notes on Multipurpose Mixes 

1. Where a fungicide (e.g., captan, 
zineb, maneb, or Karathane is mentioned 
in the text, a multipurpose spray or dust 
containing the chemical may be substi- 
tuted for the fungicide alone. 

2. Captan is the preferred fungicide for 
use on fruits, and zineb or maneb on 
vegetables. Both are good for flowers, 
trees, shrubs, and lawns. Maneb is often 
substituted for zineb on tomatoes, po- 
tatoes, celery, and certain other plants. 

3. Methoxychlor is preferred to DDT 
for use on food crops, especially within a 
month of harvest. DDT is generally more 
effective and longer-lasting. 



VEGETABLES 

zineb or maneb 
methoxychlor 
rotenone or malathion 



FRUIT 

captan 

methoxychlor 

malathion 



FLOWERS, TREES, AND 
SHRUBS 

zineb, captan, ferbam, or 

thiram 

sulfur or Karathane 

DDT or methoxychlor 

malathion 



92 



'SHOT-GUN" SOIL DRENCH 



4. Add Karathane, sulfur, Acti-dione, 
or phaltan to the vegetable and fruit 
mixes if powdery mildew becomes a prob- 
lem. 

"SHOT-GUN" SOIL DRENCH 

A "shot-gun" treatment for treating 
flats, cold frames, hot beds, cutting 
benches, or flower beds for the control 
of organisms causing damping-off, cutting 
rot, crown and root rots, and stem cank- 
ers, consists of captan plus ferbam or 
thiram and Terra clor 75 (1 tablespoon 
of each per gallon of water) . Apply as a 
soil drench using 1 pint to 1 quart per 
square foot. Some plants may be injured 
by this treatment. Check the label direc- 
tions before using. 

TO SPRAY OR TO DUST? 

There really isn't one answer to the old 
question, "Should I spray or dust my 
plants?" The answer depends on what 
you want to accomplish, how many and 
how large are the plants you wish to 
protect, how tight your budget is, and 
how much time and interest you have in 
your garden plantings. 

Many gardeners compromise and do 
both spraying and dusting. Spraying is 
done on a regular schedule. When extra 
applications are needed as a result of un- 
expected troubles or frequent rains, dust- 
ing will save time. 

Sprays are generally preferred to dusts 
by commercial growers and experienced 
gardeners because they may be directed 
easily and specifically even on rather 
windy days. No worrying, either, about 
getting dust in your eyes or on plants that 
don't need it. Spray films are more effec- 
tive and last longer than dusts, and 
materials cost less. Modern sprays do not 
leave an objectionable deposit on leaves, 
flowers, or fruit. 

Dusts are often the choice of the aver- 
age home gardener. Dusts are more 
quickly and easily applied than sprays; 
there is no messy mixing or measuring to 
worry about. Dusting can be a nuisance, 
though, if the air is not calm. Dusters 
cost less than comparable sprayers and 
are easier to carry and maintain. Dusting 
is generally impractical on large trees. 
Many gardeners prefer to dust flowers in 



the spring and vegetables throughout the 
season. Spraying is considered preferable 
for flowers in or near bloom. 

Strive for even, thorough coverage 
whether dusting or spraying. 

Modern pesticides, including fungicides, 
may often be used either as sprays or 
dusts. For spraying, insecticides come as 
emulsions or wettable powders; fungicides 
are generally wettable powders. Aerosol 
"bombs" are available for treating a few 
indoor plants. Granular insecticides are 
widely used for controlling soil insects 
or for other special uses. There are even 
small mist blowers for home gardens. 
Spray-dusters and "fog" machines are 
somewhat in between spraying and dust- 
ing. 

SPRAYERS AND DUSTERS 

There is a type and size of sprayer or 
duster designed to fit everyone's needs — 
all the way from the person with only a 
few house plants to the large estate with 
acres of gardens or orchards which need 
protection. 

Some devices are designed to serve a 
number of purposes; others are for specific 
jobs. The choice of a sprayer or duster for 
you depends on the size of the job, the 
type of application (spray or dust) de- 
sired, and the type of pesticide you use. 
Select the type of equipment that is 
within your budget and suits you best. 
Check these points when talking with your 
garden supply dealer: Does it handle and 
operate easily? Is it simple to fill and 
clean? Is it big enough for the job? Is 
the manufacturer reputable? Is it well- 
made with noncorroding parts? How long 
will it likely last if given good care? Re- 
member, price should not be your main 
consideration. 

Sprayers 

Most sprayers now have a number of 
accessories and special fittings available 
to meet practically every situation. These 
include special nozzles, extension rods, 
extra hose, spray booms, pressure tanks, 
and special rubber-tired carts. Rust-free 
models — stainless steel, brass, or copper — 
will last longer than cheaper tinplate or 
galvanized models. For covering fruit and 
shade trees you'll need high pressures 



SPRAYERS AND DUSTERS 



93 



(200 to 600 pounds or more per square 
inch) . If the sprayer does not have an 
agitator, shake the solution as you spray. 

Most gardeners prefer to have a sepa- 
rate sprayer, properly labeled, just for 
chemically controlling weeds. Many of 
the new weed killers, especially the 
hormone types, e.g., 2,4-D and 2,4,5-T, are 
extremely difficult to get completely out 
of sprayers. Check with your local county 
extension service on how to decontami- 
nate sprayers in which 2,4-D or related 
materials have been used. USDA Farmers' 
Bulletin No. 2004, Using 2,4-D Safely, 
covers this subject in detail. 

Clogging of spray nozzles can often be 
prevented by making up spray solutions 
in a thin, smooth batter of water and 
spray powder, then wash through fine- 
mesh cheesecloth or a silk stocking into 
the spray tank. Don't lay sprayer parts 
(e.g., plunger cylinder and nozzle) where 
they can pick up dirt or grass clippings, 
which might later clog the nozzle. 
Household Sprayers (capacity 4 ounces 
to 1 gallon) . Buy a type which shoots a 
continuous mist or fine spray and which 
has an adjustable nozzle. They are cheap, 
versatile, easy to operate, but limited to 
small jobs and the spray carries only a 
short distance. Coverage is difficult on 
underleaf surface. Frequent shaking is 
necessary to keep heavy suspensions from 
settling out. 





Fig. 54. Household sprayer. Continuous 
pressure type with a fully adjustable 
nozzle and three-quart capacity. (Courtesy 
Universal Metal Products Company) 



Fig. 55A. A three-gallon, easy-rolling, 
compressed air sprayer simple to fill, 
empty, and pump. Note the special noz- 
zle for spraying the lawn. (Courtesy Uni- 
versal Metal Products Company) 

Compressed Air Sprayers (1 to 5 gallons) . 
Popular. Useful for a variety of jobs 
around the home, yard, and garden. Air 
is compressed into the tank above the 
spray liquid by a hand-operated air 
pump. Low-priced and easy to operate. 
Choose one with an open or funnel-type 
mouth, pressure-relief top, chemical-resist- 
ant hose, curved extension rod, and ad- 
justable nozzle. Uncomfortable to carry 
over the shoulder, but some new models 
have a cart with rubber wheels. The 
normal operating pressure ranges from 
about 30 to 80 pounds and is maintained 
by occasional pumping. Use caution in 
opening the sprayer while there is still 
air pressure in the tank. Each sprayer is 
usually equipped with an assortment of 
nozzle discs to provide different spray 
patterns — solid cone, hollow cone, flat 
fan in fine or coarse spray, and solid 
stream. 

Some models have carbon dioxide 
(C0 2 ) cylinders to provide operating 
pressure. These cylinders discharge up to 
15 gallons of spray material at a uniform 
spraying pressure. They may be refilled 
at moderate cost. 




Fig. 55B. A three-gallon compressed air sprayer with roto-spray, adjustable nozzle 
which is available in galvanized steel or stainless steel. (Courtesy H. D. Hudson Manu- 
facturing Company) 



SPRAYERS AND DUSTERS 



95 




Fig. 56. Knapsack sprayer with five-gallon 
capacity. Has dasher type agitator with a 
metal shield and comfort back. Its spray 
pressure goes up to 100 pounds. (Courtesy 
H. D. Hudson Manufacturing Company) 



Knapsack Sprayers (2 to 6 gallons) . Easy- 
pumping. Straps on back. Delivers a fine, 
continuous mist further than the compres- 
sed-air type but is more expensive. Buy 
type with agitation system to prevent sus- 
pension settling out. Heavy to carry for 
a lady. The pump handle on some models 
may be attached at either side permitting 
right-hand or left-hand pumping. Uni- 
form spray pressures range from 80 to 
180 pounds. Some models have a metal 
shield to prevent direct body contact with 
the cold tank surface. 
Slide Pump or Trombone Sprayers. Rela- 
tively inexpensive, smooth, telescoping 
pumps which spray continuously. Spray 
carries a good distance (tops of medium- 
sized trees) . Comes attached to a i/ 2 gallon 
glass jar or a hose which dips into a 
bucket. Buy a type with specially treated, 
rust-resistant metal and an extension. 
Slide may become sticky in time. Tiring to 
use for a long time. Delivers pressures 
up to about 180 pounds. 



Wheelbarrow, Cart, and Barrel Sprayers 
(7 to 50 gallons) . Similar but generally 
have larger and more powerful pumps 
than the slide pump. Made in a variety of 
designs mounted on various types of 
frames (e.g., wheelbarrow, horizontal or 
vertical cart, bucket or barrel) . Cart or 
wheelbarrow models have 2, 3, or 4 
wheels for easy transport. A moving, 
large, full sprayer is difficult to maneuver 
on soft, wet, or unlevel soil. Continuous 
high pressures, up to about 250 pounds, 
may be developed for spraying medium- 
sized trees. Spraying is easier with two 
people: one spraying and the other man- 
ning the pump handle. 

Some cart sprayers have a special pres- 
sure tank which is precharged with a tire 
pump or at a filling station. One "charge" 
gives about 10 minutes of continuous 
spraying at a constant, desired pressure 
of up to 200 pounds. 
Garden Hose Sprayers are screwed on the 
end of your garden hose and water sup- 
plies the pressure. Add concentrated pest- 
icides to a glass or polyethylene jar at- 
tached to the garden hose. The spray gun 
attached to the lid meters out the spray 
concentrate from the jar by suction and 
mixes it with water from the hose flowing 
through the gun. A quart jar of concen- 
trate spray will make a number of gallons 
of dilute spray. Most models use liquids 
or wettable powders. Materials may not 
be applied at a constant rate. Hose pres- 
sure may not be sufficient to break spray 
into a fine mist. Adding detergent to the 
spray will help. Use is limited to the 
garden area that can be reached with the 
hose. 




Fig. 57A. A slide type brass sprayer at- 
tached to a glass jar. Shoots any spray 
from a fine mist to 25-foot stream. The 
nozzle rotates 360 degrees for easy spray- 
ing. (Courtesy Root-Lowell Corporation) 




Fig. 57B. A brass trombone spray with "gun" grip which shoots a fine mist to a 25- 
to 30-foot spray stream, up to 180 pounds pressure. It comes with 6 feet of % inch red 
plastic hose. The type shown here has a built-in 15-inch extension that telescopes in 
or out of the sprayer. It sprays with continuous pressure. (Courtesy H. D. Hudson 
Manufacturing Company) 



[96] 




Fig. 58. Wheelbarrow sprayer (17y 2 gallons). This powerful, high pressure pump de- 
livers up to 250 pounds pressure. Note the pressure tank (optional), pressure gauge, 
and tank cover to prevent spillage. (Courtesy H. D. Hudson Manufacturing Company) 



[ 97] 



98 



SPRAYERS AND DUSTERS 




- < .' 




Fig. 60A. Horizontal, 10-gallon sprayer 
which is mobile, easily filled and cleaned, 
and produces high, constant pressure. It 
comes with 15 feet of hose and spraying 
gun. (Courtesy of Oakes Manufacturing 
Company, Inc.) 



Fig. 59. Garden hose-end sprayer of ten 
gallon capacity which is made of shatter- 
proof polyethylene plastic and is light- 
weight, quick, low cost, and handy. Get 
one like this with finger-tip siphon control 
and capacity markings for accurate pro- 
portioning. (Courtesy H. D. Hudson Manu- 
facturing Company) 

Small Power Sprayers (7 to 50 gallons) . 
Wheelbarrow or estate types are available 
which vary greatly in design and special 
features. A gasoline engine with a power- 
ful 1- or 2-cylinder pump generally de- 
livers from 1 to 5 gallons of spray per 
minute at a pressure of 20 to 400 pounds. 
Pressure is regulated accurately. Get a 
large-wheeled, easily maneuverable model 
with extra hose, agitator, and adjustable, 
trigger-control spray gun. This sprayer is 
excellent for small orchards, large gar- 
dens, and estates, but is relatively ex- 
pensive. It is not economical of spray 
material. Some types may have such fea- 
tures as a trailer or tractor hitch for haul- 
ing, a spray boom for row-crop spraying, 
and skid mount. 




Fig. 60B. Erect, 12 1 /2-gallon sprayer with large, easy-rolling wheels, adjustable pres- 
sure regulator, and constant, mechanical agitator. (Courtesy H. D. Hudson Manufacturing 

Company) 



100 



MAINTENANCE OF SPRAYERS 



MAINTENANCE OF SPRAYERS 

Carefully follow the manufacturer's 
recommendations and instructions for lub- 
rication, operation, and maintenance 
which accompany the sprayer. Before 
starting a new power sprayer, check all 
designated points for proper lubrication. 
Operate the sprayer at slow speed using 
water while checking the delivery system, 
operation of control valves, and the pres- 
sure regulator. 

All types of sprayers should be 
thoroughly rinsed when changing to a 
different type of spray solution. Clean im- 
mediately after each use by pumping at 
least two changes of clean water through 
the system. Store funnel-top sprayers in an 
upside down position with the hand 
pump removed. 

Several times during the season, clean 
hand sprayers more thoroughly by filling 
the spray tank with hot water and let 
stand for a few minutes. Where possible, 
take apart and clean the pump, extension 
tubes, nozzle parts, and shut-off valve. 
Wash strainers and nozzle parts with kero- 
sene. Use an old toothbrush or a jet of 
compressed air. Replace washers that have 
become worn and nozzle discs that have 
enlarged holes. Reassemble and pump 
water through the open nozzle head to 
flush out the discharge line. Finally, pump 
to full pressure and check hose and gasket 
for leaks. Be sure the shut-off valve is 
working properly. If the pump fails to 
develop full pressure, remove the plunger 
to the cylinder and reshape the leather 
so that it seals tightly. 

Household sprayers require little care 
or maintenance. If the pump should lose 
its compression, pull the pump handle all 
the way out and add a few drops of oil 
in the air hole at the end of the pump 
cylinder. This lubricates the plunger cup 
or leather. 

Leave hand sprayers partially unassemb- 
led for the winter. Metal parts should be 
lightly oiled and wrapped in newspaper. 
The tank should be clean and dry. 

For power sprayers, follow the manu- 
facturer's directions regarding proper lub- 
rication and any special care required. 
Clean the sprayer after each use. Drain 
and flush the tank with clean water. Take 
apart the nozzles and strainers and wash 



them with kerosene. Before reassembling, 
pump water through the discharge system 
until it comes out clean. 

After spraying is completed in the fall, 
soak nozzles and strainers (screens) in 
kerosene. Run wire through the spray 
rods. Rinse hoses clean and put where 
they will not crack or freeze. 

After cleaning, and before putting a 
power sprayer away for the winter, pour 
at least a pint of new or used oil in the 
tank. Fill with water and start the pump. 
As the water is discharged, a thin coating 
of oil covers the inside of the tank, pump, 
valves, and circulating system. Finally 
drain the sprayer completely and store 
in a dry place. 

Dusters 

Of simpler construction than compar- 
able sprayers with fewer parts to go 
wrong. For maximum protection and 
safety, dust only when the air is calm 
(this may mean early morning or eve- 
ning) . Don't dust if plants are wet — 
you'll get unsightly deposits! 
Plunger Type Dusters (capacity i/ 2 to \i/ 2 
pounds of dust) . Easy to operate and 
handy for treating small areas with little 
waste. Choose one with a dust chamber 
made of metal or glass. Larger models 
with an extension tube and adjustable 
nozzle or deflector cap are much handier 
to use. Avoid the "salt shaker," flick, plas- 
tic squeeze, and telescoping cardboard 
carton types. They may be convenient for 
small jobs but generally do not provide 
uniform coverage. 

Small Bellows, Crank, or Rotary-Fan Dust- 
ers (i/2 to 5 pounds) . Easy to use and 
gives better coverage than the plunger 
type. Ideal for continuous dusting of 
small or large gardens. It is cheap, light- 
weight, faster than spraying. It may be 
difficult to direct dust exactly where you 
want it. Small models require frequent 
refilling. Get the type with an adjustable 
feed control. The duster may be carried 
in front by shoulder straps. 

Knapsack Dusters (5 to 25 pounds) . Suit- 
able for large gardens and estates. Throws 
up a steady, fine cloud of dust. Covers 
large areas rapidly without refilling. 
Lightweight, simple to use. General types: 
Bellows type (strapped on back) and the 




Fig. 61. Plunger type duster which holds about 1 pound of dust. The long 21-inch ex- 
tension with all-angle swivel deflector makes dusting simple. It discharges a uniform 
cloud. (Courtesy of H. D. Hudson Manufacturing Company) 



:: 'l|ll|H||||||HH| 




'•'• 




: ' fFTTT 






Fig. 62A. This easy turning crank duster holds about % pound of dust, light and com- 
pact, emits a fine, uniform cloud of dust. Nozzle is adjustable to any angle. 
(Courtesy H. D. Hudson Manufacturing Company) 



[102] 




Fig. 62B. This easy turning crank duster 
holds about 14 pounds of dust yet is easy 
to carry. The agitator assures even flow. 
It has a fan-shaped, adjustable nozzle 
which can dust to front or rear. (Courtesy 
H. D. Hudson Manufacturing Company) 



Fig. 63. Knapsack duster. Holds about 
17 pounds of dust. It has a built-in filler 
scoop in cover. It is easily carried on the 
back and is ideal for spot dusting or com- 
plete coverage. (Courtesy H. D. Hudson 
Manufacturing Company) 



**£. 




[103] 



104 



MAINTENANCE OF DUSTERS 



Rotary-fan type (carried in front by 
shoulder straps and operated with a 
hand crank) . Delivery tubes and nozzles 
are adjustable for both height and direc- 
tion. Buy the type with a long extension 
tube and flaring "fish-tail" nozzles. They 
are more expensive than hand dusters, 
but may be used for either intermittent 
or continuous dust applications. 
Small Power Dusters (60 to over 200 
pounds) . Practical for large gardens, 
small orchards, or estates. Small models 
(weighing 40 to 67 pounds) are carried 
on the back; larger ones are powered by 
an engine or tractor. The metering de- 
vice (or feed regulator) may be adjusted 
to apply from 5 to 50 or 100 pounds of 
dust per acre. Covers large areas rapidly 
without refilling. Wasteful of material, as 
dust often blows onto other plants. Buy 
the type with an agitator. Power dusters 
vary greatly in the size of the dust hop- 
per, type and capacity of the fan, type of 
distribution system, horsepower, and 
mounting. 

MAINTENANCE OF DUSTERS 

Follow the manufacturer's directions 
regarding operating instructions and lu- 
brication of moving parts. Use graphite 
for lubricating the steel rod and plunger 
in hand plunger dusters. Oil stains the 
equipment. 

Empty and clean the duster after using 
to prevent caking, clogging, and eventual 
corrosion. All slip joints should be given 
a protective coating in the fall before 
storing over winter in a dry place. The 
fan on power dusters should be operated 
at recommended speeds. 

For an excellent discussion of sprayers, 
dusters, their operation and uses, obtain 
a copy of Sprayer and Duster Manual, 
published by the National Sprayer and 
Duster Association, Room 1500, 300 South 
Wells St., Chicago 6, Illinois. 

SPREADERS, STICKERS, AND WETTING 
AGENTS 

The purpose of these materials is to 
help suspend the pesticide in the spray 
solution, improve the cohesiveness of the 
spray or increase the wetting of leaves by 
the spray, or all three. All commercial 
pesticides now have one or more of these 
materials already in the spray mix. 

The adding of a commercial or home- 



made spreader-sticker or wetting agent is 
recommended before spraying glossy, 
hard-to-wet foliage like roses, gladiolus, 
carnation, iris, tulip, onion, cabbage, pea, 
rhododendron, and mountain-1 a u r e 1 . 
These materials also aid in controlling 
powdery mildews and insects with a waxy 
coating like woolly aphids and mealybugs. 

Commercial spreaders (wetting agents) 
that ensure wetting of hairy or glossy fo- 
liage include Santomerse, Tween-20, 
Fluxit, and household soaps or detergents 
(e.g., Dreft, Tide, Vel, and Liquid Lux) . 
Spreaders are used at the rate of i/ A to 1 
teaspoon per gallon. 

Common stickers that allow pesticides 
to adhere tenaciously to plant surfaces in- 
clude powdered skim milk, wheat or soya 
flour, fish oil, or casein. Use 1 tablespoon 
of wheat flour per gallon. Goodrite P.E.P.S. 
is a good commercial sticker. 

Commercial spreader-stickers are avail- 
able under many trade names — among 
them Du Pont Spreader-Sticker, Filmfast, 
Nu-Film, Ortho Spreader-Sticker, Orthex 
Spreader- Adhesive, Triton B-1956, Sterox, 
and Plyac Spreader-Sticker. Most of the 
commercial spreader-stickers are used at 
the rate of 14 to ]/ 2 teaspoon per gallon. 

PARTIAL LIST OF FUNGICIDE 

MANUFACTURERS AND 

DISTRIBUTORS PLUS LEADING 

SPRAYING AND DUSTING 
EQUIPMENT MANUFACTURERS 

Acme Quality Paints, Inc., 8250 St. Aubin 
Ave., Detroit 11, Mich. 

Allied Chemical Corp., General Chemical 
Div., 40 Rector St., New York 6, N.Y. 

American Cyanamid Co., Agric. Chemi- 
cals Div., P.O. Box 672, Princeton, N.J. 

Antrol Garden Products, Boyle-Midway, 
22 East 40th St., New York 16, N.Y. 

Barco Mfg. Co., Inc., 119 Dewey St., Wor- 
cester, Mass. 

Bradson Company, 2165 Kurtz St., San 
Diego, Calif. 

California Spray-Chemical Corp., Lucas 
and Ortho Way, Richmond, Calif. 

Champion Sprayer Co., 6509 Heintz Ave., 
Detroit 11, Mich. 

Chemley Products Co., 5744 N. Western 
Ave., Chicago 45, 111. 

Chipman Chemical Co., Inc., P.O. Box 
309, Bound Brook, N.J. 




Fig. 64. Power duster. Holds about 25 pounds of dust, yet is easily carried on a man's 
back. It dusts up to 25 feet high and can also be used for mist spraying. (Courtesy H. 
D. Hudson Manufacturing Company) 



106 



MANUFACTURERS 



W. A. Cleary Corp., Box 749, New Bruns- 
wick, NJ. 

Doggett-Pfeil Co., Springfield, N.J. 

The Dow Chemical Co., Midland, Mich. 

Eastern States Farmers' Exchange, Inc., 26 
Central St., West Springfield, Mass. 

E. I. du Pont de Nemours & Co., Grasselli 

Chem. Dept. or Industrial and Biochemi- 
cals Dept., Wilmington 98, Del. 

Faesy & Besthoff, Inc., 25 E. 26th St., 
New York 10, N.Y. 

Hayes Spray Gun Co., 98 No. San Ga- 
briel Blvd., Pasadena, Calif. 

H. D. Hudson Mfg. Co., 1589 East Illi- 
nois St., Chicago 11, 111. 

Imperial Chemical Co., Shenandoah, 
Iowa. 

Mallinckrodt Chemical Works, 2nd and 
Mallinckrodt Sts., St. Louis 7, Mo. 

Miller Chemical & Fertilizer Corp., 2226 
N. Howard St., Baltimore 18, Md. 

Miller Chemical Co., 525 N. 15th St., 
Omaha 2, Nebr. 

Morton Chemical Co., Agricultural 
Chemical Division, 110 N. Wacker Dr., 
Chicago 6, 111. 

Niagara Chemical Div., Food Machinery 
& Chemical Corp., 100 Niagara St., 
Middleport, N.Y. 

The Oakes Mfg. Co., Inc., 516 Dearborn 
St., Tipton, Ind. 

Olin Mathieson Chemical Corp., Mathie- 
son Bldg., Baltimore 3, Md. 



Charles Pfizer & Co., Inc., 630 Flushing 
Ave., Brooklyn 6, N.Y. 

Pittsburgh Plate Glass Co., Corona 
Chemical Div., Moorestown, N.J. 

Rohm & Haas Co., 222 W. Washington 
Square, Philadelphia 5, Pa. 

Root-Lowell Corp., 445 N. Lake Shore 
Drive, Chicago 11, 111. 

Shell Chemical Corp., Agr. Chemicals 
Sales Div., 460 Park Ave., New York 
22, N.Y. 

Sherwin-Williams Co., 1113 Guild Hall 
Bldg., 101 Prospect Ave. N. W., Cleve- 
land 1, Ohio. 

D. B. Smith Sc Co., 483 Main St., Utica 2, 
N.Y. 

Stauffer Chemical Co., 380 Madison Ave., 
New York 17, N.Y. 

Tennessee Corp., 619 Grant Bldg., At- 
lanta 1, Ga. 

Thompson-Hay ward Chemical Co., 2915 
Southwest Blvd., Kansas City 8, Mo. 

The Upjohn Co., 301 Henrietta, Kalama- 
zoo, Mich. 

Union Carbide Chemicals Co., Div. 
Union Carbide Corp., 180 S. Broad- 
way, White Plains, N.Y. 

Universal Metal Products Co., Saranac, 
Mich. 

U.S. Rubber Co., Naugatuck Chemical 
Div., Naugatuck, Conn. 

Vaughan Seed Co., 601 W. Jackson Blvd., 
Chicago, 111. 

Westbrook Mfg. Co., St. Joseph, Mich. 



SECTION 4 



Home and Garden Plants and 
Their Diseases 



African-violet 109 

Anemone 112 

Apple 114 

Ash 124 

Avocado 127 

Barberry 129 

Bean 131 

Beet 136 

Begonia 139 

Bellflower 140 

Birch 142 

Bittersweet 1 43 

Blueberry 145 

Boxwood 150 

Cabbage 154 

Cactus 161 

Calla 162 

Camellia 164 

Canna 167 

Carnation 169 

Carrot 171 

Celery 175 

Chrysanthemum 181 

Citrus 187 

Cockscomb 189 

Corn 190 

Cucumber 196 

Currant 201 

Cyclamen 203 

Daffodil 204 

Delphinium 208 

Dogwood 211 

Elm 217 

Ferns 223 

Fig 224 

Forsythia 226 

Fuchsia 228 

Gardenia 228 

Gentian 230 

Geranium 231 



Gladiolus 232 

Grape 237 

Heath 243 

Holly 245 

Hollyhock 246 

Honeylocust 248 

Horsechestnut 250 

Hydrangea 252 

Iris 254 

Ivy 257 

Juniper 259 

Lantana 263 

Larch 264 

Lawngrass 265 

Lettuce 272 

Lily 277 

Magnolia 283 

Maple 284 

Mertensia 288 

Morning-glory 290 

Oak 295 

Oleander 298 

Onion 299 

Orchids 302 

Pansy 309 

Pea 311 

Peach 315 

Phlox 327 

Pine 330 

Poplar 337 

Poppy 338 

Potato 339 

Primrose 344 

Raspberry 347 

Rhododendron 351 

Rose 356 

St.-Johns-wort 362 

Salvia 362 

Sedum 366 

Snapdragon 368 



[107] 



108 AARONSBEARD 

Snowberry 371 Tulip 399 

Spirea 374 Valerian 403 

Strawberry 375 Viburnum 404 

Sumac 380 Vinca 405 

Sweetpotato 382 Walnut 406 

Sycamore 385 Willow 411 

Tomato 389 Yew 414 



Garden plants are listed below, together with their more important diseases. 
The prevalent or serious diseases are listed first. For local or minor diseases, check 
with your extension plant pathologist or county agent. For additional information 
on the different general diseases or control measures, see sections 2 and 3 plus the 
Appendix. 

AARONSBEARD - See St.-Johns-wort 

AARONS-ROD - See Pea 

ABELIA — See Snowberry 

ABIES -See Pine 

ABRONIA - See Four-o'clock 

ABRUS-See Pea 

ABUTILON-See Hollyhock 

ACACIA — See Honeylocust 

ACALYPHA, COPPERLEAF [PAINTED, VIRGINIA] (Acalypha) 

1. Leaf Spots — Leaves variously spotted. May wither, die, and drop prematurely. 
Control: Usually unnecessary. Pick off and burn infected leaves. Space plants. In- 
crease air circulation. 

2. Red Leaf Gall — Reddish galls develop on leaves. Control: Same as for Leaf Spots. 

3. Downy Mildew — See under Calla, and (6) Downy Mildew under General Diseases. 

4. Powdery Mildew — See (7) Powdery Mildew under General Diseases. 

5. Oedema — Indoor problem. Small, rust-colored spots or overgrowths on leaves. 
Control: Avoid overwatering and high humidity. Increase air circulation. 

6. Root Rots — See under Geranium, and (34) Root Rot under General Diseases. 
May be associated with nematodes (e.g., root-lesion or meadow, root-knot) . 

7. Root-knot — See (37) Root-knot under General Diseases. 

ACANTHOPANAX, FIVE-LEAF or FIVE-FINGERED ARALIA, CASTOR ARALIA 

(Acanthopctnax, Kalopanax); AMERICAN SPIKENARD, HERCULES-CLUB, 
SARSAPARILLA, UDO (Aralia) 

1. Leaf Spots or Blight, Spot Anthracnose, Scab — Spots of various colors, sizes, and 
shapes on leaves. See (1) Fungus Leaf Spot under General Diseases. 

2. Root Rots, Stem Rot, Watery Soft Rot -See (21) Crown Rot, and (34) Root Rot 
under General Diseases. 

3. Verticillium Wilt (udo, American spikenard) —See (15B) Verticillium Wilt un- 
der General Diseases. 



AFRICAN-VIOLET 109 



4. Rust (American spikenard, sarsaparilla) — Dark, powdery pustules on the leaves. 
Control: Pick off and burn infected leaves. 

5. Powdery Mildew (sarsaparilla) — Powdery, white mold growth on the foliage. 
See (7) Powdery Mildew under General Diseases. 

6. Twig and Branch Cankers, Dieback (Hercules-club) — Twigs and branches die 
back from discolored, girdling cankers. Control: Pick off and burn affected parts. 
Make cuts several inches below any sign of infection. 

7. Wood Rot (Hercules-club) — See under Birch, and (23) Wood Rot under General 
Diseases. 

ACHILLEA — See Chrysanthemum 

ACHLYS-See Barberry 

ACIDANTHERA - See Gladiolus 

ACONITE, ACONITUM-See Delphinium 

ACTAEA — See Anemone 

ACTINOMERIS — See Chrysanthemum 

ADAM-AND-EVE — See Erythronium 

ADAMS-NEEDLE - See Yucca 

ADDERSTONGUE - See Erythronium 

ADIANTUM-See Ferns 

AESCULUS - See Horsechestnut 

AETHIONEMA - See Cabbage 

AFRICAN DAISY -See Chrysanthemum 

AFRICAN FORGET-ME-NOT - See Mertensia 

AFRICAN-LILY - See Tulip 

AFRICAN-VIOLET (Samtpaulia); FLAME VIOLETS (Episcia); 
STARFIRE (Gesner/a); GLOXINIA (Sinningia) 

1. Crown Rots, Stem Rot, Root Rots — Widespread. Soft, mushy, brown rot of crown 
and petioles. Plants sickly. Gradually or suddenly wilt, wither, and die. Plants 
are easily pulled up. See Figure 37B under General Diseases. Often associated 
with nematodes (e.g., lance, pin, root-knot, root-lesion or meadow, spiral, stubby- 
root, stylet or stunt) . Control: Plant healthy stock in sterilized soil in sterilized 
containers (see pages 437-44) . Take cuttings only from healthy plants. Root in a 
sterile medium. Avoid overwatering, overfertilizing, and deep planting. Destroy 
badly infected plants. Keep water off the foliage. Increase air circulation. Soil 
should be well-drained. Drenching the soil with ferbam (21/4 tablespoons per gal- 
lon) may be beneficial. 

2. Botrytis Blight, Gray-mold Blight, Leaf Rot, Bud Rot — Cosmopolitan. Soft, tan 
rot of crown, buds, flowers, or leaves. A coarse, gray mold may grow on diseased 
tissue. Control: Keep down the humidity and increase the air circulation. Avoid 
overwatering and overcrowding. Destroy fading blooms promptly. Spray with 
zineb during humid weather. Control mites with malathion dips or sprays. 



110 AFRICAN-VIOLET 

3. Ringspot — General. Whitish to bright yellow rings, arcs, and streaks on the upper 
leaf surface. Control: Keep cold water off the foliage. Avoid sudden temperature 
changes. Keep plants out of direct sunlight for an hour before watering. 

4. Root-knot — General. Plants sickly, make poor growth. Small, irregular, knotlike 
galls on the roots, crowns, stems, and even the leaves. Leaves are often thickened 
and blistered. Control: Plant only disease-free cuttings in sterilized soil in sterilized 
containers. Remove and burn badly infested plants. 

5. Leaf Scorch, Chlorosis— Leaves pale to yellow and may appear as if scorched by 
fire. Control: Keep plants out of bright sun, and away from the heating effects of 
large incandescent light bulbs. 

6. Powdery Mildew — Whitish-gray mold patches on the leaves and flowers. Flowers 




Fig. 65. Powdery mildew of 
African-violet 



may be deformed and discolored. See Figure 65. Control: Destroy old infected 
leaves and flowers. Space plants farther apart. Remove old leaves close to the soil. 
Dip or spray with Karathane (i/ 2 teaspoon per gallon) plus a spreader-sticker. 
Two applications, 10 days apart, should be sufficient. Otherwise same as for Botrytis 
Blight (above) . 

7. Mosaic — Leaves crinkled and thickened. May show irregular light and dark green 
blotches. Plants may be stunted. Flowers are reduced in size and number. Control: 
Destroy infected plants. 

8. Bud Drop — Flower buds shrivel, turn brown, and drop before opening. Control: 
Avoid low temperatures and air humidity, overwatering, gas injury, and extremes 
in soil temperature, moisture, and light. Control mites and other bud pests. Check 
with your local florist or extension entomologist. 

9. Leaf or Foliar Nematode — Gradually enlarging, sunken, brown blotches between 
the leaf veins. Spots appear mostly on the underleaf surface. Plants stunted, sickly, 
may die. Control: Same as for Root-knot (above) . Remove and burn infested 
leaves. Soak potted plants in hot water (110° F.) for 30 minutes. Keep water off 
the foliage. 

10. Spotted Wilt (gloxinia) — Large, brown-ringed patterns with green centers on the 
leaves. Leaves may die. Control: Destroy infected plants. Spray with DDT or 
malathion to control thrips which transmit the virus. 

11. Aster Yellows (gloxinia) —Plants slightly yellowish. Produce numerous secondary 
shoots and no flowers. Control: Same as for Spotted Wilt. Use DDT or malathion 
to control leafhoppers which transmit the virus. 

12. Sclerotinia Blight of Gloxinia — California. Soft, rapid rot of the flowers which 
causes them to collapse. When infected flowers drop on the leaves, the rot moves 
into the leaves and then down the petioles. The growing point may be killed, 



ALUMROOT 1 1 1 



stunting the plant. Control: Pick off and burn rotting flowers when first found. 
Apply Terraclor to the soil following the manufacturer's directions. Same as for 
Crown Rot (above) . 
IS. Petiole Rot — Leaves wilt and wither from a rotting of the petioles where they 
touch the salt-encrusted pot. Control: Cover pots with aluminum foil or other 
material. 

AGAPANTHUS - See Tulip 

AGAVE — See Centuryplant 

AGERATUM — See Chrysanthemum 

AGLAONEMA - See Calla 

AGROPYRON — See Lawngrass 

AGROSTEMMA - See Carnation 

AILANTHUS - See Tree-of-Heaven 

AIR POTATO -See Yam 

AJUGA, BUGLEWEED (Ajuga) 

1. Crown Rot, Southern B Ugh t — Serious in shady, wet, poorly drained areas. Plants 
suddenly wilt and die in warm, humid weather. Bases of stems in patches rot and 
turn black. Frequently covered with a cottony mold growth. Control: See under 
Delphinium. Apply Terraclor (PCNB) to the soil surface a week before plant- 
ing. Follow the manufacturer's directions. 

2. Root-knot — Plants may be sickly and stunted with knotlike galls on the roots. 
See (37) Root-knot under General Diseases. 

ALBIZZIA - See Honeylocust 

ALDER -See Birch 

ALKANET-See Mertensia 

ALLIONIA-See Four-o'clock 

ALLIUM -See Onion 

ALLSPICE - See Calycanthus 

ALMOND -See Peach 

ALOE, HAWORTHIA 

I. Root Rot — Serious nursery disease. See under Geranium. Control: Plant in light, 
well-drained soil. Avoid overwatering. Clean infected aloe plants and soak them 
in hot water (115° F.) for 20 to 40 minutes. Plant treated plants in clean or 
sterilized soil (pages 437-44) . 

ALPINE CURRANT -See Currant 

ALTERNANTHERA - See Cockscomb 

ALTHAEA -See Hollyhock 

ALUMROOT - See Delphinium 



1 1 2 ALYSSUM 

ALYSSUM-See Cabbage 

AMARANTH, AMARANTHUS - See Cockscomb 

AMARYLLIS, AMAZON-LILY - See Daffodil 

AMELANCHIER-See Apple 

AMERICAN BLADDERNUT (Staphylea) 

l.Leaf Spots — Spots of various sizes, shapes, and colors on leaves. Control: Collect 
and burn fallen leaves. Keep plants well pruned. If practical, spray during spring 
and summer rainy periods using zineb, maneb, or captan. 

2. Twig Blights — Twigs blighted. May die back. Control: Prune out and burn af- 
fected parts. Otherwise same as for Leaf Spots. 

3. Sooty Blotch — See (12) Sooty Mold under General Diseases. 

AMERICAN COWSLIP -See Primrose 

AMERICAN LINDEN -See Linden 

AMERICAN SPIKENARD - See Acanthopanax 

AMORPHA - See False-indigo 

AMPELOPSIS - See Grape 

AMSONIA-See Vinca 

ANAGALLIS — See Primrose 

ANAPHALIS — See Chrysanthemum 

ANCHUSA-See Mertensia 

ANDROMEDA [ FORMOSA, JAPANESE, MOUNTAIN ] (Pierls) 

1. Leaf Spots, Tar Spot — Small spots on leaves in which black dots may later be 
sprinkled. Control: Apply zineb, maneb, or ferbam sprays at 2-week intervals, 
starting when leaves are half grown. 

2. Root Rot, Dieback — Roots decay. Plants gradually decline, wither, die back, and 
finally die. Often associated with nematodes (e.g., bloat, lance, pin, reniform, 
ring, root-lesion, spiral, stubby-root, stunt or stylet) . Control: See under Apple, 
and (34) Root Rot under General Diseases. 

ANDROSACE — See Primrose 

ANEMONE [JAPANESE, POPPY, AND WOOD], PASQUEFLOWER, 

WINDFLOWER (Anemone;,- BANEBERRY [ RED, WHITE ] (Acfaej; 

RUE-ANEMONE (Anemone/la); BUGBANE, BLACK-SNAKEROOT or 

BLACK COHOSH (Cimic/fi/ga); LIVERLEAF (Hepatlca)} GLOBEFLOWER 

(Trollius) 

1. Leaf Spots — Spots of various sizes, shapes, and colors on leaves. Leaves may dis- 
color and drop early, usually starting at the base of the plant. Control: Space 
plants. If serious, apply maneb, zineb, fixed copper, ferbam, or captan at about 10- 
day intervals during wet weather. Destroy infected plant parts as soon as found. 
Burn tops in the fall. 

2. Rusts — Powdery, brown pustules or "orange cluster cups" on the lower leaf surface. 



ANEMONE 113 



Affected plants do not flower. Leaves may be stunted, thickened, crowded, turn 
pale and fleshy. Alternate hosts include plums, cherries, and various grasses. Con- 
trol: Dig out and burn infected anemone plants as they will not recover. Spray 
or dust as for Leaf Spots (above) . Propagate from disease-free plants. 

3. Downy Mildew — Widespread on anemone. Large brown or black blotches on 
leaves. Corresponding undersides of leaves are covered with delicate, white mildew 
patches. Leaves tend to roll upwards. Plants distorted. Control: Same as for Leaf 
Spots (above) . 

4. Leaf and Stem Smuts — Irregular, dark brown to black, powdery blisters and 
streaks on swollen regions of leaves and leaf stalks. Common on wood anemone. 
See Figure 66. Control: Same as for Rusts (above) . 



'WmWw'-P^MmMim 



Fig. 66. Anemone smut. 




5. Leaf Gall, Spot Disease (anemone) — Flowers, stems, and leaves spotted with 
small red warts. Flowers may become dwarfed, distorted, and fall early. Control: 
Same as for Leaf Spots (above) . 

6. Leaf and Stem Nematode — Dark brown or black blotches on leaves. Leaves may 
die. Control: See (20) Leaf and Stem Nematode under General Diseases. 

7. Powdery Mildew (anemone, rue-anemone) — See (7) Powdery Mildew under 
General Diseases. 

8. Crown Rot, Rhizome Rot, Southern Blight (anemone) — Underground parts or 
stem rots at the soil line. Plants wilt, wither, and collapse. Control: Completely 
dig out and destroy infected plants together with 6 inches of surrounding soil. 
Sterilize remaining soil with heat or chemicals. See "Soil Treatment Methods and 
Materials" in the Appendix. 

9. Botrytis Collar Rot (anemone) — Crowns rotted and destroyed near the soil line. 
Flowers and flower buds may rot. Control: Avoid crowding plants. Plant in light, 
well-drained soil. Spray as for Leaf Spots (above) . 

10. Mosaic, Flower Breaking (anemone) — Leaves mottled light and dark green. May 
show some yellowing. Flowers may show light or off-color streaks and blotches. 
Control: Destroy infected plants. Keep down weeds. Control the aphids which trans- 
mit the virus, using lindane or malathion. 

11. Aster Yellows — See (18) Yellows under General Diseases. 

12. Spotted Wilt (anemone) —See (17) Spotted Wilt under General Diseases. Con- 
trol: Same as for Mosaic (above) . Spray with DDT and malathion to control 
thrips, which transmit the virus. 

13. Root-knot — See (37) Root-knot under General Diseases. 



114 ANEMONELLA 

ANEMONELLA - See Anemone 

ANETHUM-See Celery 

ANGELICA; TAENIDIA 

i.Leaf Spots — General. Spots of various sizes, shapes, and colors on the leaves. If 
severe, leaves may wither. Control: Collect and burn tops in the fall. Space plants. 
If severe, apply zineb, maneb, or ferbam at about 10-day intervals during rainy 
weather. 

2. Rusts — Yellow, orange, reddish-brown or black, powdery pustules on leaves. Con- 
trol: Same as for Leaf Spots (above) . 

3. Root Rot — See (34) Root Rot under General Diseases. 

ANGELS-TRUMPET - See Tomato 

ANGRAECUM - See Orchids 

ANISE, ANISE-ROOT - See Celery 

ANISETREE - See Magnolia 

ANNUAL BLANKET-FLOWER - See Chrysanthemum 

ANODA-See Hollyhock 

ANTENNARIA, ANTHEMIS-See Chrysanthemum 

ANTHONY WATERER-See Spirea 

ANTHRISCUS - See Celery 

ANTHURIUM-See Calla 

ANTIRRHINUM - See Snapdragon 

APIUM-See Celery 

APPLE, CRABAPPLE [ARNOLD, BECHTEL'S, CARMINE, CHARLOTTE'S, 

CHINESE FLOWERING, CUTLEAF, ELEY'S, GARLAND or WILD SWEET, 

HALLIS, HYBRID, JAPANESE FLOWERING, KAIDO, MANDSHURIAN, 

PARKMAN'S, PRAIRIE, PURPLE, RIVERS', SARGENT, SCHEIDECKERI, 

SIBERIAN, SOULARD, SOUTHERN, TEA, TORINGO ] (Malus); SERVICEBERRY 

[ALLEGHANY, APPLE, CLUSTER, CUSICK, DOWNY, WESTERN], JAPANESE 

JUNEBERRY, JUNEBERRY, SHADBLOW, SHADBUSH (Amelanchier); 

CHOKEBERRY [ BLACK, PURPLE, RED ] (Aronia); FLOWERING QUINCE 

[ DWARF JAPANESE, JAPANESE, CHINESE QUINCE ] (Chaenomeles); 

HAWTHORN or THORN [ ARNOLD, COCKSPUR, DOTTED, ENGLISH, FLESHY, 

LAVALLE'S, PAUL'S DOUBLE SCARLET, RED HAW or SCARLET, 

WASHINGTON ] (Crataegus); COTONEASTER [ BEARBERRY, BOXLEAF, 

COIN-LEAF, CRANBERRY, CREEPING, HUPEH, MANYFLOWER, NECKLACE, 

PEKING, ROCK or QUINCEBERRY, ROCKSPRAY, SMALL-LEAF, SPREADING ] 

(Cofoneasferj; QUINCE (Cydonia); LOQUAT (Eriobotrya); MEDLAR 

(Mespilis); CHINESE PHOTINIA, CHRISTMASBERRY, ORIENTAL PHOTINIA, 

TOYON (Photinia); FIRETHORN [ ENGLISH, FORMOSA, SCARLET, YUNNAN ] 

(Pyracanffia;,- PEAR [ BIRCH-LEAF, COMMON, SAND, SNOW ] (Pyrus); 

MOUNTAIN-ASH [AMERICAN, CHINESE, COLUMNAR, EUROPEAN or 

ROWANTREE, KOREAN, PACIFIC, PYRAMIDAL, SHOWY, SHRUBBY CHINESE, 

WEEPING, WESTERN ], WHITE BEAMTREE, SERVICETREE (Sorbus); 

CHINESE STRANVAESIA (Stranvaesia) 

I.Leaf Spots — General. Spots of various sizes, shapes, and colors on the leaves. If 



APPLE 



115 



blackened and blasted at temperatures above 65° F. New shoots suddenly appear as 
if scorched by fire. Brown or blackened leaves cling to the twigs. Slightly sunken, 
discolored cankers on the twigs, branches, and trunk. Often followed by Black 
Rot and wood rots. See Figure 40 under General Diseases and Figure 67. Control: 
Avoid overstimulation of trees. Plant in fertile, well-drained soil. Follow the spray 
program in the Appendix (Table 10) . Prune out cankers 3 to 4 inches back into 
healthy wood. Prune during the dormant season or in late summer if hot and 
dry. Apply disinfectant and then tree wound dressing (page 25) to cut surfaces. 
Swab pruning tools with 70 per cent denatured alcohol between cuts. A 1:1,000 
solution of mercuric chloride may also be used. Fairly resistant apples: Anoka, 
Arkansas Black, Chestnut, Crimson Winesap, Dutchess, Early Winesap, Fenton, 
Fireside, Haralson, Jonadel, King David, Mcintosh, Minjon, Northern Spy, North- 
western Greening, Prairie Spy, Red Delicious, Redwell, Sharon, Stayman Red, 
Turley, Virginia, Winesap, and Yellow Delicious. Fairly resistant crabapples: 
Alney, Arnoldiana, Arrow, Atrosanguinea, Coronaria charlottae, Cowichan, Dolgo, 



HEALTHY 





DISEASED 



Fig. 67. Fire blight (blossom blight) of 
Japanese quince. 





Fig. 68. A. Photinia leaf spot, B. Photinia 
scab. 



Floribunda, Gloriosa, Hopa, Jay Darling, Mahamik, Red Silver, Sargenti, Sissi- 
puk, Van Eseltine, and Whitney. Fairly resistant pears: Anjou, Baldwin, Carrick, 
Dabney, Ewart, Farmingdale, Funks Colorado, Hood, Kiefler, Lincoln, Magness, 
Mendel, Moe, Moonglow, Morgan, Nectar, Old Home, Oregon 18, Orient, Pine 
Apple, Pontotoc, Richard Peters, Seckel, Tyson, Vistica, Waite, Winter Nellis, and 
Wurtenburg. Numerous resistant cotoneaster and pyracantha species and varieties 
are also available. Check with your local nurseryman or extension horticulturist 
regarding the adaptability of these varieties to your area. Spraying 2 or 3 times 
during the bloom period with streptomycin (60 to 100 parts per million) or 
zineb may control the blossom blight stage. Follow the manufacturer's directions. 
Do not use streptomycin on Cotoneaster racemiflora or Crataegus mollis. See also 
(24) Fire Blight under General Diseases. More effective sprays should be available 
soon. 
2. Scab — Widespread and serious. Dull, smoky spots which change to a velvety, 
olive-green color. Finally become brown to black and often scaly. Spots occur on 



116 



APPLE 



leaves and fruit as well as flower parts. Fruit may be deformed and cracked. Many 
young fruit and leaves drop early. See Figure 28C under General Diseases, and 
Figure 68B. Control: Collect and burn fallen leaves in autumn. Follow a regular 
spray program using a multipurpose fruit spray containing captan, zineb, or thiram. 
Dodine (Cyprex) is widely used by commercial growers. See the spray schedule in 
the Appendix (Table 10). Apple and pear varieties differ in susceptibility. Check 
with your local nurseryman. Resistant crabapples: Coronaria charlottae, Dolgo, 
Floribunda, Gloriosa, Halliana, Parkmani, Katherine, Makamik, Sargenti, Sissi- 
puk, Van Eseltine, Zumi, and many others. Resistant firethorn: Yunnan. 
3. Rusts — Widespread. Pale yellow, yellow-orange to orange-red spots (with black 
specks) on the upper leaf surface with a mat of creamy-white, light orange to 




Fig. 69. Hawthorn rust (early infection). 



Fig. 70. Apple blotch on leaf and twigs. 
(Courtesy Dr. V. H. Young) 



brown tendrils forming on the corresponding underleaf surface. Heavily spotted 
leaves drop early. Yellowish to reddish or greenish areas on fruit, usually near 
the calyx end. Fruit may be distorted and drop early. Twigs and small branches 
may die back. See under Juniper Rusts. See Figure 22C under General Diseases 
and Figure 69. Control: Follow the regular spray program as for Scab. Add 1 
tablespoon of ferbam, zineb, or thiram (Thylate) to each gallon of spray from 
prebloom through second cover (see Table 10 in the Appendix) . Varieties differ 
in resistance to the several rusts. Check with your nurseryman, county agent, 
extension horticulturist or plant pathologist. Resistant apples: Arkansas Black, 
Cortland, Delicious, Dutchess, Haralson, King David, Mcintosh, Macoun, North- 
western Greening, Sharon, Turley, York, Winesap, and Wolf River. Destroy nearby, 
worthless, erect junipers, redcedars, cypress, incense-cedar, or white-cedar which 
show rust galls. 
4. Black Rots, Frog-eye Leaf Spot, Dieback (primarily apple, crabapple, pear, quince, 



APPLE 117 

flowering quince, hawthorn, cotoneaster, and mountain-ash) — Expanding, brown, 
zoned spots on the fruit which often start at insect wounds or mechanical injur- 
ies. Fruits later turn into shriveled, black mummies which cling to the twigs. Leaf 
spots are purple, then gray with a purple margin. Rough-barked cankers on twigs 
and large limbs, which often die back. Commonly follows Fire Blight. Control: 
Follow the regular spray program using captan, thiram, or zineb plus methoxychlor 
and malathion. Avoid wounding trees. Prune out dead wood and destroy rotted 
fruit mummies. Plant disease-free nursery stock. 

5. Crown Gall — General. Rough, dark, corky gall on the trunk near the soil line, 
at graft union and on roots. Trees gradually lose vigor, may later die. See Figure 
44A under General Diseases. Control: Plant disease-free stock with a smooth 
graft union. Avoid wounding young trees, especially near the soil line. Destroy 
badly infected trees. See (30) Crown Gall under General Diseases. 

6. Infectious Hairy Root, Woolly Knot — Widespread. Most common in the nursery. 
Primary roots are swollen and often extend some distance from a basal gall be- 
fore secondary fibrous roots are produced. Excessive growth (tufts) of these long, 
fine, fibrous roots gives a woolly appearance. Bacteria enter only through wounds. 
Small fibrous roots occur singly or in clusters at the base of the trunk, crown, 
or roots. May be associated with Crown Gall, with a mass of fleshy roots arising 
from a gall. May be confused with burr knot (a noninfectious proliferation of 
roots) characteristic of certain varieties. Control: See Crown Gall (above) . 

7. Powdery Mildews — General. Whitish-gray, powdery mold or felty patches on 
young leaves, buds, blossoms, and twigs. Leaves may be crinkled, curled, dwarfed, 
narrowed, and erect. Shoots stunted with rosette-type growth. May die back. 
Fruits russeted. Control: Where common, follow the apple spray program using 
sulfur or Karathane in prebloom sprays through first cover. Grow resistant va- 
rieties. Check with your county agent, extension horticulturist or plant patholo- 
gist. 

8. Sooty Molds or Blotch, Fly Speck — General. Irregular, sootlike spots or clusters 
of 6 to 50 "fly specks" on the surface of fruit or twigs. Follows attacks by aphids, 
scales, and other insects. See Figure 26 under General Diseases. Control: Follow 
the regular spray program (Table 10 in the Appendix) . Add zineb in midsum- 
mer and late summer sprays or alternate zineb and captan from second cover 
on. Prune to open up trees. 

9. Blotch (apple, crabapple) — Irregular, dark brown to black, somewhat sunken 
spots on the fruit. Small, rough cankers may girdle the twigs and fruit spurs. 
Small, round, white spots occur on the leaves in which a single, black speck 
develops. Spots may run together. See Figure 70. Control: Same as for Black Rots 
(above) . Resistant apple varieties: Grimes Golden, Jonathan, Stayman Winesap, 

and Winesap. 
10. Root Rots — Foliage thin. Leaves often turn yellow, wither and drop prematurely. 
Growth is slow. Twigs and branches die back. Fruit crop often is heavy just 
before the tree dies. Coarse white to black mold fans or strands often grow 
just under the bark of the lower trunk and on root surfaces. Clumps of honey- 
colored mushrooms may appear near the trunk base. See Figure 47B under General 
Diseases. Control: Plant in fertile, well-drained soil where root rot of woody 
plants has not occurred before. Remove dying trees, including the roots. Do not 
replant in the same location for a number of years. Control rodents and borers. 
Check with your extension entomologist or county agent. Fertilize, water, and 
follow the recommended spray program to maintain tree vigor. Soil fumigation 
in the fall with carbon disulfide has been used to control Armillaria Root Rot 



118 



APPLE 



(Oak-root Fungus Disease) . This is a job for an experienced arborist. Carbon 
disulfide is inflammable and explosive. 

11. Fruit Spots and Rots — General. Small to large, round to irregular, watersoaked, 
light tan to black spots on and in the fruit. Decay may later be covered with a 
white, blue, green, pink, black, dark brown, or gray mold. Rots often enter in- 
sect or mechanical injuries. Develop rapidly in warm, moist storage. See Figure 
46A under General Diseases. Control: Follow the regular spray program, es- 
pecially in late cover sprays. Adding zineb to sprays often helps. Control insects by 
using methoxychlor and malathion. Apply captan alone just before harvest. Pick 
early before many fruit drop. Handle fruit carefully. Store only sound, blemish- 
free fruit just above freezing. Apple varieties differ in resistance. 




Fig. 71. Apple twig canker. (Iowa State 
University photo) 



12. Twig, Branch, and Trunk Cankers, Northwestern Anthacnose, Limb Blight — Af- 
fected bark is often sunken, roughened, and discolored with wood underneath 
dead and discolored. Round to irregular cankers often girdle twig, limb, or 
trunk killing parts beyond. Entire tree may die. Cankers often show zoned 
ridges. Varieties differ in susceptibility. Check with your local nurseryman, ex- 
tension horticulturist or plant pathologist. Most common on weakened trees 
low in vigor. See Figure 71. Control: Prune out and burn cankered twigs and 
branches. Cut out large cankers and sterilize cuts with household bleach or a 
1:1,000 solution of mercuric chloride (see page 85 for precautions). Then paint 
with a tree wound dressing. Follow the regular spray program to control insects 
and other diseases. Avoid wounding branches and trunk. Maintain vigor by 



APPLE 



119 



fertilizing in the spring and watering during dry periods. Wrap young trees to 
prevent sunscald. Where serious, a spray of 4-4-50 bordeaux is recommended af- 
ter leaves drop in the fall. 

IS. Wood Rots, Butt Rots, Collar Rots, Heart Rots — See under Birch, and (23) 
Wood Rot under General Diseases. Collar rot causes killing of the bark and 
wood underneath at or near the soil line. Trees may be girdled and killed. Con- 
trol: Follow the regular apple spray program. Control borers by spraying the 
trunk and scaffold limbs with lead arsenate or DDT. Check with your county agent 
or extension entomologist regarding rates to use and dates of application for your 
area. 

14. Winter Injury, Collar Rot — Roots, shoots, twigs, or buds may be killed. Split- 
ting of the bark is common, especially on the trunk. See Figure 72. Generally 



Fig. 72. Winter injury to 
a young apple tree. 
(Iowa State University 
photo) 




occurs on the south or southwest side. Sometimes results from failure of wood 
to mature in the fall, excessively low temperatures, and other factors. Control: 
Same as for Sunscald (below) and Wood Rots (above) . 
15. Sunscald — Most common on young, exposed trees. Freezing injury to the trunk 
and larger branches on the south or southwest side and where fruit are exposed 
to direct sun during hot, dry weather. Dark patches occur on pear leaves in mid- 
summer. Control: Wrap young trees and exposed larger branches (Figure 12) 



120 APPLE 

with burlap, or sisalkraft paper. Follow spray program (Table 10 in the Appendix) . 
Maintain trees in vigorous condition. Water during summer droughts. Do not 
prune off lower limbs for several years. Leave lowest limb on the south side. 

16. Fruit Breakdowns in Storage (Scald, Bitterpit, Baldwin or Jonathan Spot, Black 
End, Brown Core or Heart, Soggy Breakdown or Soft Scald, Water Core) — May 
be caused by an irregular water supply during the season, general unthrifty 
growth, an unbalance or lack of essential soil nutrients, toxic vapors given off 
by the fruit in storage, freezing injury, poor storage conditions and other factors. 
Control: Check with a local grower or your extension horticulturist. Have the 
soil tested. Prune, water, and fertilize trees to keep them vigorous. Pick fruit 
when first mature. Place in a cold, well-ventilated storage place as soon as pos- 
sible. 

17. Leaf Spots, Leaf Blight, Anthracnose — Leaves variously spotted, may turn color 
and drop early. Fruit and twigs may be spotted. Varieties differ in susceptibility. 



jjte 



i^lfrii 






**^> A $? *W$ : ^W^ $ ^i~ i< F'9- 73 - Hawthorn leaf blight. 






IP" 



English hawthorn, especially the variety Paul's Scarlet, is very susceptible to Leaf 
Blight. Cockspur and Washington hawthorns are resistant. Control: Cut out and 
burn blighted twigs. Collect and burn fallen leaves. Follow the spray program as 
for Scab (above) or use zineb. Maneb, ferbam, Acti-dione, or phenyl mercury 
may be used on hawthorn. Apply at about 2-week intervals. Start when the new 
leaves appear. See figures 68A and 73. 

18. Stony Pit of Pear - Mostly Pacific Coast states. Symptoms variable. Small, dark 
green areas on young fruit which later develop into deep "pits." Fruit may become 
deformed, gnarled, and woody at maturity. Foliage is reduced. Control: Destroy 
infected trees. Plant resistant varieties (e.g., Bartlett — a symptomless carrier) 
propagated from virus-free stock. Varieties showing mild symptoms include Clair- 
geau, Old Home, Packham's Triumph, and Waite. 

19. Witches' -broom, Black Mildew of A melan ch ier — Widespread. A mass of sturdy 
new shoots form witches'-brooms. Leaves usually coated with a black mold. Con- 
trol: Cut off and burn witches'-brooms. 



APPLE 121 

20. Mistletoe (apple, hawthorn, pear) — See (39) Mistletoe under General Dis- 
eases. 

2.\.Root Nematodes (e.g., burrowing, dagger, lance, needle, pin, root-lesion or mea- 
dow, sheath, spear, spiral, stunt, stubby-root) — Tree vigor is reduced. Leaves are 
stunted. Terminal growth may die back. May be associated with root rot and 
"little leaf" or rosette. Small, dead, dark spots on the white rootlets. Affected 
roots may be stunted and distorted. Control: Keep trees as vigorous as possible 
through feeding, pruning, and watering. Fumigate soil (pages 440-44) before re- 
planting. 

22. Root-knot — Common in southern states, especially where cover crops have been 
used. Knots and swellings on the roots which may be confused with those made 
by woolly apple aphids, crown gall, and hairy root. Plants may be stunted. Foliage 
yellowish with scorching of the leaf margins. Leaves may wilt temporarily in 
hot, dry weather. Control: Same as for Root Nematodes (above) . 

23. Apple Mosaics — Leaves variously mottled (light and dark green mosaic) with 
many small, irregular, white to creamy yellow flecks, spots, and patches. Leaf 
veins may be banded by white or pale yellow stripes. Symptoms extremely variable 
on a single tree or even a single branch. A few mottled leaves may appear on an 
otherwise healthy-appearing branch. Large numbers of leaves may drop early. 
Viruses are spread by underground root grafts. Control: Destroy wild apples 
near the orchard. Plant certified, virus-free stock. Follow the spray program in 
Table 10 in the Appendix. 

24. Apple Flat Limb — Slight depression or furrow on twig or limb which becomes 
more pronounced with age. Bark over the depression is smooth. Affected branches 
are often brittle; may break under a fruit load. Control: Same as for Apple Mo- 
saics (above) . 

25. Apple Rubbery Wood — Twigs and smaller branches bend over or "weep" from 
their own weight. Wood is soft and "cheesy" in texture when cut. Affected trees 
are stunted, less vigorous than normal. Symptoms often restricted to certain 
branches of a tree. Fruit appear normal, but yield is reduced. Some varieties are 
symptomless carriers of the virus. Control: Same as for Apple Mosaics (above) . 

26. Zinc Deficiency, Little Leaf — Common in alkaline soils on apple and pear. 
Whorls of small, stiff, yellowish, sometimes mottled leaves (called rosettes) at 
tips of current season's growth. Twigs are usually spindly and stunted. May die 
back after the first year. Control: Check with your county agent or extension horti- 
culturist. They may recommend a dormant spray of zinc sulfate. 

27. Internal Cork, "Drought Spot" or Dieback, Boron Deficiency (apple, pear) — 
Widespread and may be serious in local areas. Large, more or less superficial 
dead areas, which become russeted and cracked, usually appear before the apple 
fruit is half grown. Brown corky spots form in the fruit flesh. Twigs die back 
in late summer. Leaves on the current season twigs are yellowish with red veins. 
Somewhat cupped and distorted. Dead areas develop at the tips and margins. 
Normal buds fail to develop or make poor growth. Twigs may form witches'- 
brooms. Pear blossoms may be blasted. Control: Add borax to the soil around 
trees or spray with boric acid (0.1 to 1 per cent) following the recommendation 
of your extension horticulturist or a local grower. Spraying during bloom with 
Solubor has also given good results on apple. 

28. Leaf Scorch, Potassium or Calcium Deficiency (apple, pear) — Leaves on many 
varieties develop marginal scorching, browning, and shriveling about the mid- 
dle of the growing season. A yellow or red discoloration is characteristic of cer- 
tain varieties. Twigs are slender and stunted. May die back. Fruit poor, pale in 



122 APRICOT 

color and "woody." Similar scorching may be caused by drought, strong dry 
winds and a water-logged or "shallow" soil. Control: Have the soil tested and 
apply a potash or calcium-containing fertilizer as recommended. Varieties differ 
greatly in susceptibility. 

29. Pear Decline — Widespread and serious in the Pacific Northwest. Plants are stunted 
and make little or no new growth. Trees gradually decline, wilt, and die. Foliage 
on affected trees is sparse and often turns a dull to bright red prematurely. Bart- 
lett, D'Anjou and other varieties on oriental and imported French rootstocks 
are most susceptible. Failure or poor union between the scion and rootstock. 
Roots die back. The cause is still in doubt but poor cultural practices, unusual 
growing conditions, soil fungi, and nematodes may be contributing factors. An 
insect- or mite-borne virus may also be involved. Control: Replant using resistant 
rootstocks (e.g., virus-free Old Home) . Check with your extension or state plant 
pathologist regarding the latest available information. 

30. Thread Blight — Southeastern states. See under Walnut. 

31. Felt Fungus (apple, hawthorn, pear) —Southern states, on neglected trees. See 
under Hackberry. Control: Follow the recommended spray program. 

32. Leaf Blister, Witches' -broom (amelanchier) — California. See (10) Leaf Curl un- 
der General Diseases. 

APRICOT -See Peach 

AQUILEGIA - See Delphinium 

ARABIAN-TEA - See Bittersweet 

ARABIS — See Cabbage 

ARACHIS-See Peanut 

ARALIA — See Acanthopanax 

ARAUCARIA, NORFOLK ISLAND PINE, MONKEYPUZZLE TREE, 
BUNYA-BUNYA (Araucaria) 

I.Branch Blight, Dieback — Tips of lower branches die back. Later, entire branches 
are killed. Tip ends bend and break off. The disease gradually spreads upward 
killing the tree. Control: Prune off and burn infected branches when first noticed. 
Spraying with a fixed copper fungicide during spring and fall rainy periods may 
be beneficial. 

2. Crown Gall — Smooth, roughly circular galls, up to an inch in diameter, occur at 
or near the soil line. Control: Avoid wounding tree base when cultivating, mow- 
ing, etc. 

3. Root Rot — See under Apple, and (34) Root Rot under General Diseases. 

4. Leaf Spots — Leaves spotted. Unimportant. 

ARBORVITAE - See Juniper 

ARBUTUS, ARCTOSTAPHYLOS - See Blueberry 

ARCTOTIS — See Chrysanthemum 

ARECASTRUM - See Palms 



ASCYRUM 123 



ARENARIA-SEE Carnation 

ARENGA-See Palms 

ARGEMONE-See Poppy 

ARGYREIA — See Morning-glory 

ARISAEMA-See Calla 

ARISTOLOCHIA, BIRTHWORT, DUTCHMANS-PIPE, VIRGINIA SNAKEROOT 

(Aristolochia) 

1. Leaf Spots — Spots of various colors, sizes, and shapes on leaves. Control: Apply 
ferbam, zineb, or maneb several times, 10 to 14 days apart, starting when the 
leaves are \/± inch out. 

2. Gray-mold Blight — See (5) Botrytis Blight under General Diseases. Control: Spray 
as for Leaf Spots. 

3. Root Rot — See under Geranium. Plant in light, well-drained soil. Avoid over- 
watering. 

ARMERIA — See Sea-lavender 

ARNICA — See Chrysanthemum 

ARONIA — See Apple 

ARROWROOT - See Rabbit Tracks 

ARROWWOOD - See Viburnum 

ARTEMISIA — See Chrysanthemum 

ARTICHOKE - See Lettuce 

ARTILLERY-PLANT (Pilea) 

1. Leaf Spots — Round to angular, gray or tan spots on the leaves. Spots may enlarge 
and run together forming large blotches. Older infected leaves may turn yellow 
and drop early. Control: Pick off and burn infected leaves. Space plants. Indoors, 
keep water off the foliage and avoid high humidity. If needed, spray several times, 
10 days apart, using fixed copper or maneb. 

2. Powdery Mildew — Grayish-white mold blotches on the leaves. Control: If serious 
enough, apply sulfur or Kara thane several times, 10 days apart. 

3. Root Rot — See under Geranium, and (34) Root Rot under General Diseases. 
Control: Indoors, plant in well-drained, sterilized soil. See pages 437-44 in the Ap- 
pendix. Avoid overwatering and overfertilizing. 

4. Root-knot — See (37) Root-knot under General Diseases. 

ARUNCUS-See Rose 
ASCLEPIAS — See Butterflyweed 
ASCYRUM - See St.-Johns-wort 



124 



ASH 



ASH [BLACK or HOOP, BLUE, EUROPEAN, FLOWERING, GREEN, 

OREGON, RED, VELVET, WHITE] (Fraxinus); 

FRINGETREE [AMERICAN, CHINESE or ORIENTAL] (Chionanthus); 

FORESTIERA, SWAMP-PRIVET (Forestiera) 

1. Rusts (ash, forestiera) —General. Twigs and petioles may be swollen. Leaves are 
distorted. Bright yellowish-orange, powdery pustules appear on affected parts. 
Infected leaves may wither and drop early. Another rust on forestiera, causes 
reddish-brown to black, powdery pustules on the leaves. See Figure 74. Control: 




Fig. 74. Ash rust. 



Avoid growing ash and forestiera where the alternate hosts, cord and marsh 
grasses (Spartina spp.) , are abundant. If serious enough, spray three times at 
2-week intervals, starting about when apples are in bloom. Use ferbam, zineb, 
ziram, dichlone, bordeaux mixture, or sulfur. 

2. Leaf Spots, Anthracnose — Widespread during wet springs. Small to large, round 
to irregular spots and blotches of various colors develop on the leaves, particularly 
between the veins and along the edges. Leaves may be distorted, wither, and drop 
early. Control: Collect and burn fallen leaves. If practical, spray several times, 
10 days apart, starting as the buds swell. Use zineb, ferbam, phenyl mercury, ziram, 
captan, or fixed copper. 

3. Leaf Scorch (primarily ash) — Margins of leaves turn brown following hot, dry, 
windy weather. Dead areas advance inward between the leaf veins. Most prevalent 
throughout the top of the tree or on the windward side during July and 
August. Control: Prune to open up the tree. Fertilize to increase vigor. Water dur- 
ing dry periods. 

4. Twig Blight, Dieback, Branch and Trunk Cankers — General. See under Maple 
and Elm. Control: Prune out and burn infected twigs and branches. Keep trees 
growing vigorously through fertilizing, watering during summer droughts, and con- 
trolling other disease and insect pests. Avoid wounding bark. Paint wounds 
promptly with a tree paint. 

5. Wood Rots — Widespread. See under Birch, and (23) Wood Rot under General 
Diseases. 

6. Crown Gall, Hairy Root (ash) — See under Apple, and (30) Crown Gall under 
General Diseases. 



ASPARAGUS 125 

7. Powdery Mildews — Widespread from late summer on. Grayish-white, powdery, 
mold patches on the leaves and young twigs. Leaves may turn yellow and drop 
early. Control: See under Birch. 

8. Root Rot — See under Apple. 

9. Verticillium Wilt (ash) —See (15B) Verticillium Wilt under General Diseases. 

10. Sooty Mold, Black Mildew — Black mold patches on the leaves. Control: Spray to 
control insects. Use DDT and malathion plus a fungicide. 

11. White Ash Flower Gall — Clusters of very irregular, bunchy, brown galls on male 
(staminate) flowers. The galls, caused by minute mites, are conspicuous during 
the winter months. Control: Apply malathion after the buds swell and before 
the new growth emerges in the spring. 

12. Root-knot — See under Peach. 

13. Mistletoe — See (39) Mistletoe under General Diseases. 

14. Felt Fungus — Southeastern states. Purple-black, feltlike growth on the bark. As- 
sociated with scale insects. See under Hackberry. 

15. Seedling Blight — See under Pine. 

ASIMINA — See Pawpaw 

ASPARAGUS, GARDEN; 

ASPARAGUS-FERN or LACE-FERN, "SMILAX" OF FLORISTS, 

SPRENGER ASPARAGUS (Asparagus) 

l.Rust (asparagus) —General. Yellow to orange-red, then black, powdery pustules 
on the stems and leaves. Top may die early, reducing next year's crop. Control: 
Plant normally rust-resistant Mary Washington or Martha Washington and Cali- 
fornia 500. Destroy volunteer plants or wild asparagus near producing beds. Cut 
and burn tops in the fall. Asparagus species vary greatly in resistance. If prac- 
tical, apply zineb or maneb just after harvest and continue at 10-day intervals to 
midsummer. Start spraying young, uncut beds in midspring. Acti-dione may also 
be used following the manufacturer's directions. Elgetol or Krenite may be used in 
the fall or spring on dormant plants. Follow the manufacturer's directions. 

2. Fusarium Wilt, Yellows, Foot and Root Rot — Plants stunted, turn yellow, wilt, 
and gradually die (decline) . Spears gradually decrease in size and number. 
Roots and shoot bases show red or reddish-brown streaks and flecks when cut 
through. Poor stand. Control: Plant treated seed (Table 13) or healthy stock in 
a clean, well-drained, well-prepared soil as far from old beds as possible. Plow 
under unproductive beds. Keep plants growing vigorously by watering and ferti- 
lizing. 

3. Branchlet Blight, Stem Cankers, Dieback (asparagus, asparagus-fern) — Branchlets 
wither and fall. Plants may die back to the crown. Pale cankers, often sprinkled 
with black dots, may occur on the stems. Control: Collect and burn tops in the 
fall. Where practical, apply maneb or z : neb sprays before wet periods, 7 to 10 
days apart. Avoid overwatering. Plant in sterilized (fumigated) soil, where practical. 

4. Crown Gall — Irregular, thick, pale green, fleshy gall at base of stem. See (30) 
Crown Gall under General Diseases. Control: Plant healthy stock in soil which 
has not had the disease in 3 years or more. Dig up and destroy infected plants. 

5. Leaf (Branchlet and Stem) Spots — Small, generally oval to elliptic, spots on stems, 
branches, and needles. Spots are tan to gray with a reddish-brown border. Needles 
and youngest branches may die and drop early. Control: Same as for Rust (above) . 
Keep plants growing vigorously by watering and fertilizing. Apply zineb, maneb, 
or captan at weekly intervals during rainy periods. 



126 ASPARAGUS-BEAN 

6. Stem Rots, Crown Rot — Watery, soft spots or rot of shoots. Often near the soil 
line. Tissues may be covered with a gray, cottony, or blue-green mold growth. 
Spots often enlarge rapidly. Tops wilt, may collapse. See (5) Botrytis Blight, (21) 
Crown Rot, and (29) Bacterial Soft Rot under General Diseases. Control: Keep the 
soil surface loose and dry. Carefully dig up and destroy infected plants and sev- 
eral inches of surrounding soil. Plant in well-drained soil. Avoid overcrowding 
and wounding stems. Applying Terraclor (PCNB) to the soil surface before 
rots start may help. See under Bean. Protect seedlings for winter by slight hilling 
in autumn. Avoid injury when harvesting. 

7. Root-knot — See under Bean, and (37) Root-knot under General Diseases. 

8. Chlorosis — Normal green color fades to yellow. Control: Avoid overwatering and 
too acid or alkaline soil. 

9. Verticillium Wilt — See (15B) Verticillium Wilt under General Diseases. 
10. Root Rots — See (34) Root Rot under General Diseases. May be associated with 

nematodes (e.g., lance, needle, pin, spiral, stem, stylet or stunt) . 

ASPARAGUS-BEAN - See Pea 

ASPARAGUS-FERN - See Asparagus 

ASPEN -See Poplar 

ASPIDISTRA, CAST-IRON PLANT (Aspidistra) 

1. Chlorosis and Root Rot — Leaves turn yellow and die. Control: Avoid overwater- 
ing and too much light. Plant in well-drained soil. 

2. Leaf Spots, Leaf Blight, Anthracnose — Spots of various sizes, shapes, and colors 
on the leaves. If the disease is severe, leaves may wither and die. Control: Pick 
off and burn infected leaves. Spray as for Leaf Spots of Chrysanthemum if that is 
practical. 

ASPLENIUM - See Ferns 

ASTER (CHINA- and HARDY) - See Chrysanthemum 

ASTILBE 

1. Powdery Mildew — See (7) Powdery Mildew under General Diseases. 
, 2. Fusarium Wilt — Plants turn yellow, wilt, and die. Control: Set out healthy plants 
j in clean or sterilized soil. Avoid injuring roots and crown. 

ATAMASCO-LILY - See Daffodil 

ATHYRIUM-See Ferns 

AUBRETIA-See Cabbage 

AUCUBA, JAPANESE AUCUBA, GOLDDUST-TREE (Aucuba) 

1. Leaf Spots — Brown or black spots, often zoned. Mostly near margins of leaves. 
Infected leaves may wither and drop early. Control: Spray several times, 10 days 
apart, using zineb, maneb, or fixed copper. Combine with an insecticide (e.g., 
DDT or malathion) to kill scales, if these insects are present. 

2. Gray-mold Blight — Indoor problem where moist. Twigs blighted and killed back. 
Affected areas may be covered with a dense gray mold in damp weather. Control: 






AVOCADO 127 

Space plants. Keep the humidity down. Increase air circulation. Keep water off 
the foliage. 

3. Anthracnose, Wither Tip — Spots develop on leaves and flowers. Stem cankers 
cause tips of branches to wilt and die back. Control: Pick or cut off affected plant 
parts. Apply zineb, captan, or maneb before wet periods. 

4. Verticillium Wilt — See (15B) Verticillium Wilt under General Diseases. 

5. Frost or Winter Injury — Easily mistaken for disease. Young leaves are nipped by 
spring frosts. Older leaves turn brown in winter in northern states unless pro- 
tected. Check with your local nurseryman or extension horticulturist regarding 
winter protection. 

AUTUMN-CROCUS - See Colchicum 

AVENS-See Rose 

AVOCADO, REDBAY, SWAMPBAY (Persea); CAMPHOR-TREE, CINNAMON- 
TREE (Cinnamomum); SPICEBUSH (Lindera or Benzoin); CALIFORNIA- 
LAUREL (Umbellularia); POND-SPICE (Litsea); SASSAFRAS 

1. Root Rots — Cosmopolitan on avocado and camphor-tree. Trees gradually or sud- 
denly decline in vigor and productivity. Leaves are pale, tend to wilt, and drop 
early. Branches die back. Trees may die. Often serious in wet, poorly drained 
soils. See under Apple. Control: Treat suspected avocado seed before planting 
by soaking for 30 minutes in hot water (120° to 122° F.) . Then wash in cold 
water and dry. In California, Texas, and Florida, grow resistant strains of avo- 
cado (e.g., Duke or Scott rootstocks) developed for planting in infested soils. 
Plant in deep, well-drained soil (fumigated, if possible) where root rot has not 
been present before. Indoors plant in sterilized soil. See "Soil Treatment Methods 
and Materials" in the Appendix. Maintain a uniform soil moisture supply. 

2. Wood, Heart, Trunk and Collar Rots, Trunk Cankers — Widespread. Trees may 
gradually decline in vigor or die suddenly due to a rotting and girdling of the 
trunk (collar rot) , or encircling cankers. Control: See under Birch and Dogwood. 
Avoid covering the bud union with soil. 

3. Anthracnose or Black Spot, Leaf Spots or Blotch, Leaf and Fruit Scab — General. 
Small to large, round to irregular, spots and blotches on the leaves. Leaves or 
branch tips may wilt and wither. Spots may also occur on avocado flowers and 
fruit. Fruit may appear russeted. Control: Collect and burn fallen leaves and 
spotted or scabby fruit. Otherwise same as for Twig Canker (below) . Avocado 
varieties resistant to Scab: Booth 1, Collinson, Fuchsia, Itzamna, Linda, and Wal- 
din. Varieties also differ in resistance to Cercospora Spot. 

4. Twig and Branch Cankers, Dieback — Widespread. Foliage on twigs and branches 
may wilt and wither. Twigs and branches die back from small to large, girdling, 
discolored cankers. Control: Cut off and burn affected plant parts. Avoid wounds. 
Paint over promptly with a tree wound dressing. Spray during rainy periods using 
ferbam, zineb, maneb, captan, or fixed copper. Where avocados are grown com- 
mercially, follow the recommended spray schedule for your area. Check with your 
county agent or extension plant pathologist. 

5. Oedema (avocado) — Indoor problem. Small "scabby" or wartlike growths de- 
velop on the upper leaf surface. These later crack open and become reddish- 
brown in color. Control: Avoid overwatering during moist, overcast weather. 
Increase air circulation and temperature. 



128 AXONOPUS 

6. Verticillium Wilt (avocado, camphor-tree, sassafras) — Leaves on one to several 
branches or the entire plant, wilt, turn brown, wither, and remain on the tree. 
A brown discoloration may be seen in the wood just under the bark on the 
branches and trunk. Trees may die or recover completely. Control: See under 
Maple. 

7. Sun-blotch (avocado) — Long, narrow, shallow streaks develop near the stem 
end of the fruit. The streaks are whitish or yellow in green fruits and red or 
purplish-red on purple or black varieties. Yellow streaks occur on green stems 
and branches. Older stems are uneven and rough. Shoots prostrate, willowy, 
twisted, and lack vigor. Control: Plant seed, scion wood, and rootstocks from 
virus-free trees. 

8. Little Leaf, Rosette, Zinc Deficiency (avocado) — Leaves severely mottled at edges. 
Leaf tips may appear scorched without mottling. Avocado fruit may be deformed. 
If prolonged, branches may die back. Control: Sprays of zinc sulfate (8 ounces in 
10 gallons) and hydra ted lime (4 ounces in 10 gallons) , applied soon after new 
growth appears, are often used. With many soils a single application of zinc chelate 
has given protection for 3 years or more. Check with your county agent or ex- 
tension horticulturist. 

9. Powdery Mildew — Powdery, white mold growth on underside of leaves mostly 
on trees growing in shaded, damp locations. Shoot tips may die back. Control: 
If serious enough, apply two Karathane sprays, 10 days apart. 

10. Fruit Spots and Rots — Small to large, enlarging spots on avocado fruit. Fruit may 
appear russeted, scabby, or cracked. May develop on fruit in tree or after harvest. 
Fruit often covered with black, blue, or white mold growth. Control: Follow the 
recommended spray schedule for your area (see under Twig Canker above) . Keep 
trees well pruned. Pick fruit early and store at the recommended temperature 
and humidity. Check with your extension horticulturist. 

11. Black Mildews, Sooty Blotch (avocado, California-laurel, camphor-tree, redbay, 
sassafras, spicebush, swampbay) — Primarily in the Gulf states and California. 
Black mold patches on foliage and branches. Control: Spray as for Twig Canker 
(above) . Control insects with malathion sprays. 

12. Root-knot and Other Root-Feeding Nematodes (burrowing, dagger, pin, ring, root- 
lesion or meadow, sheath, sphaeronema, stubby-root) — See under Peach. Avocado 
is resistant to Root-knot. Associated with decline and sickly foliage. 

13. Mistletoe — See (39) Mistletoe under General Diseases. 

14. Yellows (sassafras) —Leaves dwarfed and rolled. Branch tips are bunched and 
fasciated. Control: None suggested. 

15. Chlorosis, Mottle Leaf — Mostly in alkaline soils. Leaves turn yellow except for 
the veins. See under Maple. Avocado varieties differ in resistance. 

17. Seedling Blights — See under Pine. 

AXONOPUS — See Lawngrass 

AZALEA — See Rhododendron 

AZARA 

l.Stem Rot — See (21) Crown Rot under General Diseases. Control: Dig up and 
destroy infected plants. Set new plants in clean or sterilized soil (pages 437-44) . 

AZTEC LILY -See Gladiolus 

BABIANA-See Iris 



BARBERRY 129 



BABY-BLUE-EYES - See Phacelia 
BABYSBREATH - See Carnation 

BABYTEARS VINE (Helxine) 

l.Leaf Spot — See (1) Fungus Leaf Spot under General Diseases. 

2. Rust — See (8) Rust under General Diseases. 

3. Powdery Mildew — See (7) Powdery Mildew under General Diseases. 

BACHELORS-BUTTON - See Chrysanthemum 

BALDCYPRESS - See Pine 

BALLOONFLOWER - See Bellflower 

BALM — See Salvia 

BALM-OF-GILEAD - See Poplar 

BALSAM [GARDEN, SULTAN]; PATIENCE PLANT (Impatiens) 

\.Leaf Spots, Anthracn ose — Small to large spots or blotches on leaves. Leaves and 
young shoots may be blighted. Control: Apply zineb, maneb, or captan. Burn tops 
in the fall. 

2. Wilts (Bacterial and Verticillium) —See (15B and C) under General Diseases. 
Control: Destroy infected plants. Do not replant in the same soil without first 
treating with heat or chemicals (pages 437-44) . 

3. Stem Rots — Watery, soft rot at the soil line. Later covered with a cottony mold. 
Control: Same as for Wilts. 

4. Downy Mildew — See (6) Downy Mildew under General Diseases. 

5. Rust — Generally unimportant in gardens. See (8) Rust under General Diseases. 
Alternate hosts include Adoxa and wild grasses (Agrostis and Elymus) . 

6. Root-knot — Southern states. See (37) Root-knot under General Diseases. 

7. Damping-off — Seedlings wilt and collapse. Control: Sow seed in clean, well- 
drained soil or a sterile medium. Avoid overwatering. 

8. Root Rot — See under Chrysanthemum. May be associated with nematodes (e.g., 
dagger, root-knot) . 

BALSAM-APPLE, BALSAM-PEAR - See Cucumber 

BALSAMROOT (Balsamorhiza) - See Chrysanthemum 

BALTIC IVY -See Ivy 

BANEBERRY - See Anemone 

BAPTISIA — See False-indigo 

BARBERRY [BLACK, BOX, GREEN-LEAF, DARWIN, DWARF MAGELLAN, 
JAPANESE or THUNBERGS, KOREAN, MENTOR, MINIATURE, NEUBERT, 
RED-LEAF JAPANESE, ROSEMARY, THREESPINE, UPRIGHT JAPANESE, 
WARTY, WILSON, WINTERGREEN ] (Berberis); VANILLALEAF (Achlys); BLUE 
COHOSH (Caulophyllum); MAHONIA [ CASCADES, CLUSTER, CREEPING, 
LAREDO, LEATHERLEAF or CHINESE, OREGON-GRAPE or HOLLYGRAPE ] 

(Mahonia) 

1. Verticillium Wilt (barberry) —Leaves wilt, turn brown or red, wither, and fall 
on one or more branches. Inside of stems show green to brown streaks when 



130 BARBERRY 

cut. Entire plants may later die. Control: Dig up and burn severely infected 
plants. Do not replant in the same location for several years. Plant in well- 
drained soil. Avoid wounding roots and stem. Fertilize and water to stimulate 
vigor. 

2. Bacterial Leaf Spot and Twig Blight (barberry) — General. Small, round to ir- 
regular, dark green, water-soaked spots which later turn a purplish to reddish- 
brown color. Twigs may die back. Control: Prune out and burn infected twigs. 
Apply several fixed copper, bordeaux (4-4-50) , or streptomycin sprays (100 parts 
per million) , 10 days apart, starting when the new leaves open. 

3. Anthracnose , Fungus Leaf Spots, Leaf Blotch — Tan, brown, or purple spots on 
the leaves. Often with a distinct margin. Control: If serious enough, apply several 
sprays, 7 to 10 days apart, using copper, zineb, maneb, or ferbam. 

4. Powdery Mildew (barberry) — Whitish powdery mold on leaves. Control: If serious 
enough, apply several sprays, 7 to 10 days apart, using sulfur or Kara thane. 

5. Root-knot — See (37) Root-knot under General Diseases. 

6. Rusts — Small, bright orange to blood-red spots on the upper leaf surface in the 
spring. The underside of infected leaves shows golden-yellow, cuplike growths with 
fringed margins, or minute, brownish, powdery pustules. Cultivated barberries are 
highly resistant or immune to the serious stem rust of cereals and grasses of which 




Fig. 75. Stem rust on barberry. (USDA 
photo) 



the common (European) barberry, Oregon-grape, and other Mahonias are the 
alternate hosts. In many states it is unlawful to grow rust-susceptible varieties of 
barberry or Mahonia. Check with your nurseryman or extension plant pathologist 
before planting. See Figure 75. Other alternate hosts of Mahonia rusts include 
Koeleria and Oxalis. 

Root Rot - See under Apple and (34) Root Rot under General Diseases. Avoid 
heavy, poorly drained, compact soil. Space plants for good aeration and light. 



BEAN 131 

8. Mosaic (barberry) — Irregular pattern of reddish blotches on the leaves. Control: 
Destroy affected plants. 

9. Cankers, Dieback, Heart Rot — Twigs and branches die back. See under Maple. 
Control: Cut out and burn infected parts. Spray as for Anthracnose (above) . 

10. Gray-mold Blight (barberry, blue cohosh) —Blossoms and leaves are blighted. 
May be covered with a gray mold in damp weather. Control: Same as for An- 
thracnose (above) . 

11. Leaf Scorch, Scald (mahonia) —Leaves scorched by winter winds and sun in 
northern states. Control: Plant in protected locations, where adapted. Erect can- 
vas or burlap barriers to ward off winter winds. 

12. Root-feeding Nematodes (e.g., dagger, pin, ring, spiral, stem, stylet or stunt) —As- 
sociated with sickly, stunted plants in a state of decline. Control: Same as for 
Root-knot (above) . 

BASIL, BASILWEED - See Salvia 

BASKETFLOWER - See Chrysanthemum 

BASSWOOD-See Linden 

BAYBERRY-See Waxmyrtle 

BEACH PEA -See Pea 

BEAKED CORNSALAD - See Valerian 

BEAMTREE-See Apple 

BEAN [ ADZUKI, GARDEN (vine or pole, bush or dwarf), KIDNEY, LIMA, 

MUNG, SIEVA or CIVET, SCARLET RUNNER, TEPARY, TEXAS ] (Pfiaseo/us); 

JACKBEAN, SWORDBEAN (Canavalia) 

1. Bacterial Blights — General. Water-soaked blotches on leaves, stems, and pods 
which soon enlarge and become irregular and brown or reddish-brown areas 
with yellowish margins. Leaves become dry, brittle, and ragged. Stems may be 
girdled, dwarfing, or killing plants. Diseased seed may be shrunken, discolored, 
and show a varnish-like coating or appear healthy. Most severe after hail or frost 
damage. See Figure 16A under General Diseases. Control: Plant only certified, 
weakened. See Figure 21A under General Diseases and Figure 95. Control: Avoid 
plants. Keep down weeds. Space plants. Plant in well-drained soil. Maintain 
three-year rotation. Collect and burn or bury tops after harvest. Resistant bean 
varieties to one or more blights: Blue Lake, Corneli 14, Fullgreen No. 1, Great 
Northern No. 1, Kentucky Wonder, Michelite, Pinto, Red Mexican, Richmond 
Wonder, Robust, Starland Wax, Tendergreem and Tenderlong 15. Scarlet runner 
beans are normally resistant to bacterial blights. Plant lima beans as far away 
from lilac, pear, etc., as possible. 

2. Bacterial Wilts — Symptoms may closely resemble those of Bacterial Blights. Plants 
are stunted. Leaves hang limply during the heat of the day. Later turn brown 
and drop off. Infected seeds are yellow and wrinkled. Often shrunken and 
"varnished." Seedlings or older plants wilt and die. Control: Plant certified, 
western-grown seed. Rotate. Cultivate shallowly. Plant resistant bean varieties: 
Black Wax, Crystal White Wax, Golden Wax, Great Northern No. 1, Kentucky 
Wonder, Michelite, Monroe, Refugee Wax, Tendergreen, and Valentine. Lima 
beans are generally resistant. 

3. Mosaics, Mottle, Yellow Dot and Stipple, Streak — General. Leaves usually puck- 
ered, dwarfed, crinkled, and curled downward. Show irregular, yellow or light and 



132 BEAN 

dark green mottling. Plants often stunted, bunchy, and a sickly yellow color. Pro- 
duce few pods. Pods often deformed, rough, shiny (or greasy) , and stunted. See 
Figure 32C under General Diseases. Control: Plant certified, virus-free seed. Re- 
sistant bean varieties to two or more mosaic-type viruses: Blue Lake, Choctaw, 
Columbia Pinto, Contender, Corneli 14, Earligreen, Extender, Florigreen, Garden 
Green, Great Northern 1140, etc., Harvester, Idaho Bountiful, Idagreen, Ideal 
Market, Improved Brittle Wax, Improved New Stringless, Kentucky Wonder, 
Mountaineer, Red Shellout, Resistant Cherokee, Rialto, Sanilac, Sensation Ref- 
ugees No. 1066 and 1071, Seminole, Shipper, Small White 51 and 52, Stringless 
Blue Lake (Clara Val, F-M 1 and No. 231), Tenderbest, Tendercrop, Tenderlong 
15, Tenderwhite, Topcrop, Topmost, Wade, Wadex, White Seeded Contender, 
and Wisconsin Refugee. Lima bean varieties resistant to mosaic: Burpee Best, 
Burpee Improved, Carpenteria, Challenger, Detroit Mammoth, Dreer Bush, Dwarf 
Large White, Early Jersey, Fordhook, Improved No. 243, King of the Garden, 
Leviathan, McCrea, New Wonder, and Seibert. Scarlet runner beans are resistant 
to a wide range of bean viruses. Keep down weeds. Control aphids which trans- 
mit the viruses. Apply malathion at weekly intervals. Grow beans as far away 
from alfalfa, clover, sweet clover, gladiolus, lupine, and possibly corn as practical. 

4. Root Rots, Stem Cankers — General. Plants sickly and stunted with few pods. 
May wilt and die. Leaves turn yellow and drop early. Roots and stem near the 
soil line are discolored and decayed. May be associated with nematodes. See (34) 
Root Rot under General Diseases. Control: Plant certified, disease-free seed, 
treated with thiram, chloranil, or captan (see Table 13 in the Appendix). Plant 
in warm, well-drained, fertile soil where beans or related crops have not grown 
for 6 years or more. Cultivate shallowly. Keep plants growing vigorously. Burn crop 
debris after harvest. Bean varieties resistant to Fusarium Dry Root Rot: Blue 
Pod Medium, Flat Marrow, Hodson Wax, Michelite, Monroe, and Robust. Scarlet 
runner beans are also resistant to this root rot. 

5. White Mold, Watery Soft Rot, Crown Rot, Sclerotinia Wilt — General. Soft, water- 
soaked spots on leaves, stems, and pods which soon enlarge and become covered 
with a cottony mold. Stem just below the soil line is often water-soaked and 
darkened. Affected parts become mushy, wilt, and die. Most common when foliage 
is dense. Control: Avoid overcrowding and overhead sprinkling. Keep down 
weeds. Plant in well-drained soil. Apply Terraclor (PCNB) at first bloom or 
before vines shade ground. Rotate. Carefully dig up and burn affected plants. 
Partially resistant bean varieties: FM 1, Golden Wax and Stringless Green Pod. 

6. Anthracnoses — General except in dry areas in the western states. Sunken, reddish- 
brown to nearly black spots or blotches on pods and seed. Veins on the under- 
side of leaves develop blackened portions. Long, dark red cankers develop on 
the stems. May enlarge and girdle stems. Young plants may die. Control: Same as 
for Bacterial Blights (above) . Plant in well-drained soil and keep down weeds. 
No good resistant bean varieties are yet available to all fungus strains. Where 
practical, spray as for Downy Mildew (below) , especially in the seedbed, or use 
ferbam. Control insects by using a multipurpose spray containing malathion and 
DDT, methoxychlor, or rotenone. Do not use DDT within 30 days of harvest. 

7. Rust — General. Infrequent on lima bean and scarlet runner bean. Small reddish- 
brown, then chocolate-brown to black, pustules on any aboveground plant parts 
late in the season. Mostly on underleaf surface. Leaves may yellow, wither, and 
fall early. Yield is reduced. See Figure 22B under General Diseases. Control: Same 
as for Bacterial Blights (above) . Bean varieties resistant or tolerant to many rust 
races: Borinquen, Criolla, Florigreen, Golden Gate Wax, Golden "No Wilt," 
Great Northern 1140, Green Savage, Harvester, Hawaiian Wonder, U.S. No. 4 



BEAN 133 



Kentucky Wonder, Kentucky Wonder Rust Resistant, Kentucky Wonder Wax, 
Lualualei, Morse Pole No. 191, Potomac, Rialto, Rust-proof Golden Wax, Semi- 
nole, Stringless Blue Lake No. 228 and 231, Tendergreen, U.S. Pinto No. 5 and 
14, and Wade. Where necessary, make several weekly applications of maneb, 
zineb, ziram, thiram, chloranil, dichlone, or sulfur, starting when rust is first evi- 
dent. If dusting, make applications twice weekly. 

8. Powdery Mildews — Widespread. Whitish, powdery, mold patches on the leaves, 
stems, and young pods. Young leaves may curl, turn yellow, shrivel, and fall 
early. Pods may turn black. Control: Rotate. Burn or plow under plant debris af- 
ter harvest. Keep down weeds. Apply Karathane, sulfur, or Acti-dione one to 
four times weekly starting when mildew is first seen. Normally resistant bean 
varieties: Columbia Pinto, Contender, Dixie Belle, Extender, Flight, Fullgreen, 
Ideal Market, Kidney Wax, Lady Washington, Pink, Pinto, Ranger, Round Pod, 
Seminole, Stringless Green Refugee, Striped Hope, Tenderlong 15, Topcrop, 
U.S. No. 5 Refugee, Valentine, and Wade. 

9. Downy Mildew — Serious on lima bean along the Atlantic seaboard where days 
are moderately warm, nights cool, and the humidity is high. Cottony mold patches 
on the pods, young shoots, flowers, and leaves. Affected parts turn black and 
shrivel. Shoots and flowers are distorted. Control: Plant certified, western-grown 
seed. Four-year rotation. Burn crop debris after harvest. Plant in well-drained soil. 
Normally resistant lima bean varieties: New Fordhook types U.S. 156, 242, etc., 
Henderson Bush types have some resistance, Thaxter, U.S. 155, 255, 355, 1556, 
and 1558. Spray at least weekly, with maneb, zineb, captan, or fixed copper. Cop- 
per sprays may cause some pod spotting. 

10. Seed Rots, Damping-off — Seeds decay. Stand is thin and weak. Seedlings wilt and 
collapse from a rot at or below the soil line. Most serious in cool, wet weather. 
Control: Plant seed treated with thiram, chloranil, or captan plus dieldrin, lindane, 
or heptachlor (see Table 13 in the Appendix) . Plant in warm, well-drained soil. 
After planting, treat as for Cabbage Wirestem. 

11. Ashy Stem Blight, Charcoal Rot — Widespread. Mostly in southern states. Seedlings 
blacken and collapse. Slightly sunken, reddish-brown to black areas on stem at the 
soil line. The centers later turn ashy gray and become sprinkled with black dots. 
Disease spreads up the stem and down into the roots. Plants usually die before pro- 
ducing seed. Roots are decayed and blackened. Control: Plant certified, western- 
grown seed in well-drained soil. Treat seed as for Seed Rot (above) . Keep down 
weeds. Keep plants growing vigorously by proper fertilization and watering in dry 
weather. Rotate, excluding beans, gourds, watermelon, sweetpotato, pepper, potato, 
dahlia, chrysanthemum, and related plants. Collect and burn crop debris. 

12. Lima Bean Pod Spot or Blight — Atlantic seaboard. Small to large, irregular, brown 
patches on leaves. Pale brown to black watery spots may develop on the older pods. 
Affected areas may be sprinkled with minute black "pimples." Control: Plant certi- 
fied, western-grown seed. Four-year rotation. Spray as for Downy Mildew (above) . 

13. Curly-top — Western states. Leaves become puckered, cup downward. Become 
brittle, stunted, and either a darker green or yellowish. Plants dwarfed and bunchy. 
Older plants ripen early, while younger plants die quickly or gradually. Pods re- 
duced in size and number. See Figure 76. Control: Plant at the proper time for your 
area (check with your county agent or extension entomologist) to escape the spring 
migration of the beet leafhopper which transmits the Curly-top virus. Resistant 
bean varieties: Burtner's Blightless, California Pink, California Red, Columbia, 
Golden Gem, Great Northern, Idaho Bountiful, Jenkins, Pink and Red Mexican, 
Pinto, Pioneer, and Stringless Green Pod. Most lima bean varieties are fairly resist- 
ant. 



134 BEAN 




Fig. 76. Curly-top of bean. 



14. Root-knot, Cyst Nematodes — Mostly southern states. Plants stunted, yellowish, and 
sickly. Irregular, swollen galls which are enlargements of roots themselves. Cannot 
be rubbed off. Control: Rotate. Maintain vigor. Fertilize, water, keep down weeds. 
Where severe, fumigate soil in the fall with D-D, EDB, etc., following the manu- 
facturer's directions. See (37) Root-knot under General Diseases. Resistant bean 
varieties: Alabama Pole No. 1 and 2, Spartan, and State. Resistant lima beans: Bix- 
by, Hopi 155, 200, and 5989, Nemagreen, Nemagreen Bush, Westan, and certain 
Rico numbers. Jackbean and swordbean are also resistant. 

15. Other Fungus Leaf Spots, Pod and Stem Spots or Blotches, Stem Anthracnose, Lima 
Bean Scab — Spots of various sizes, shapes, and colors on the leaves, stems, and 
pods. Spots on leaves may drop out leaving shot-holes. Leaves may wither and fall 
early. Plants may be yellowish, stunted and die early. Seeds shriveled. Control: Plant 
certified, western-grown seed in well-drained soil. Keep plants growing vigorously. 
Spray as for Downy Mildew (above) . Two-year rotation or longer. Collect and 
burn crop debris after harvest. Resistant varieties (e.g., lima bean to Stem Anthrac- 
nose) may be available shortly. Refrigerate promptly after harvest. 

16. Baldhead, Snakehead — Seedlings are stumps without growing tips. Plants die or 
remain stunted. Control: Plant certified, high-quality, crack-free seed in a well- 
prepared seedbed. Treat seed as for Seed Rots (above) . Avoid deep planting. 

17. Sunscald, Leaf Scorch — Pods exposed to the hot sun show reddish or pale brown 
spots and streaks. Irregular, dead, brown areas form on the leaves. Control: Plant 
in well-drained soil. Control other diseases and insects. 

18. Web B light — Southeastern states. Definite, round to irregular brown spots with 
a distinct, darker border on the leaves and pods. Spots are of variable size. Under 
moist conditions leaves are a scalded, light green color. Later the whole leaf turns 
gray to brown and dies. Other leaves and stems soon die. Stems are girdled by en- 
larging, tan to brown cankers. Diseased foliage may be held together (webbed) by 
delicate, whitish fungus hyphae. Control: Same as for Root Rots (above) . Spray as 
for Downy Mildew (above) . 

19. Fusarium Yellows, Wilts — Western states. The lower leaves, especially on one side 
of the plant, gradually turn yellow. The disease progresses upwards with the older 
leaves turning yellow and dropping off. Plants may die. Stems show brown streaks 
when cut. Control: Plant disease-free seed in uninfested soil. Lima beans are highly 
resistant or immune. Otherwise same as for Root Rots (above) . 

20. Verticillium Wilt — See (15B) Verticillium Wilt under General Diseases. 



BEECH 135 

21. Spotted Wilt, Ringspot — Plants may die outright or leaves die one by one. See 
(17) Spotted Wilt under General Diseases. 

22. 2,4-D Injury — See under Grape. Beans are very susceptible. 

23. Other Root-feeding Nematodes (awl, dagger, lance, pin, reniform, ring, root-lesion 
or meadow, sheath, spear, spiral, sting, stubby-root, stunt or stylet) — Mostly south- 
ern states. Associated with sickly, stunted plants. Control: See under Root-knot 
(above) . 

24. Chlorosis — In alkaline or very acid soils where there is a "deficiency" of zinc, 
copper, magnesium, or manganese. Control: Have the soil tested and follow the 
recommendations. 

25. Crown Gall — See (30) Crown Gall under General Diseases. 

BEANTREE - See Goldenchain 

BEARBERRY - See Blueberry 

BEARD-TONGUE - See Snapdragon 

BEAUTYBERRY - See Lantana 

BEAUTY-BUSH - See Viburnum 

BEDSTRAW - See Buttonbush 

BEEBALM-See Salvia 

BEECH [AMERICAN or SILVER, EUROPEAN, FERNLEAF, JAPANESE, 

ORIENTAL, PURPLE, PURPLE WEEPING, PYRAMIDAL, SIEBOLD'S, 

WEEPING] (Fagus) 

1. Wood, Heart, and Butt Rots — Cosmopolitan. See under Birch, and (23) Wood 
Rot under General Diseases. 

2. Twig and Branch Cankers, Dieback — Widespread. May be serious. See under 
Maple. Control scale insects using DDT and malathion. Or apply a dormant lime- 
sulfur spray (1 to 20 dilution) . 

3. Bleeding Canker — Northeastern states. Light brown to reddish-brown liquid 

("blood") oozes from bark usually near the base. See also under Maple. Control: 
Cut down and burn severely infected trees. Avoid wounding bark and overfeeding. 
But keep trees vigorous by fertilization and watering during droughts. Injection of 
trees with "Carosel," which contains a mixture of helione orange and malachite 
green dyes, has helped check the disease. There is no cure. 

4. Powdery Mildew — Powdery, grayish-white mold on leaves and young shoots. 
Leaves may turn yellow and wither. Control: If severe enough, spray twice, 10 
days apart, using sulfur or Karathane. 

5. Root Rot — See under Apple, and (34) Root Rot under General Diseases. May 
be associated with nematodes (e.g., root-knot, spiral) . 

6. Leaf Scorch — Leaves turn brown at margins. Scorching may progress until leaves 
fall. Often follows hot, dry, windy weather. Control: Fertilize trees. Water in hot, 
dry weather. Prune to open up trees. 

7. Leaf Spots — Minor problem. See under Maple. 

8. Mottle Leaf — Northeastern states. Cause unknown, possibly a virus. Unfolding 
leaves are sprinkled with small, semitransparent spots with a yellowish-green or 
white halo. Spots enlarge, turn brown, and dry. Most common between the veins 
and along the leaf margins. Brown areas increase in size until the entire leaf is 



136 



BEET 



scorched. Leaves may drop early. A new set of normal leaves may form in mid- 
summer. The bark on the trunk and large branches may be scalded and die in 
patches. Control: Fertilize trees to maintain vigor. Protect bark from summer sun 
by wrapping with burlap or sisalkraft paper. 
9. Mistletoe — See (39) Mistletoe under General Diseases. 

10. Sooty Mold — Black moldy patches on foliage. See under Elm. 

11. Felt Fungus — Southern states. See under Hackberry. 

BEET [GARDEN, SUGAR], SWISS CHARD, LEAF or SPINACH BEET, 
MANGEL, MANGOLD (Beta); SPINACH (Spinacea); BURNING-BUSH, 
SUMMER-CYPRESS (Kochia); NEW ZEALAND SPINACH (Tetragonia) 

1. Cercospora Leaf Spot — General. Small spots with gray to brown centers and 
reddish-purple margins develop on leaves, leaf stems, flower parts, and even 




Fig. 77. Cerccspora leaf spot of beet. 



seeds. Spots may drop out leaving ragged leaves which often wither and die. Table 
beets are somewhat resistant. See Figure 77. Spinach is seldom seriously injured. 
Sugar beet varieties differ in resistance. Often most severe when plants are also 
infected with Virus Yellows (below) . Control: Three-year rotation. Burn tops or 
plow under cleanly after harvest. Plant disease-free seed or treat as for Seed Rot 
(below) . Keep plants growing vigorously by fertilizing and watering during dry 
periods. Space plants. Apply maneb, zineb, or fixed copper at 2-week intervals 
in rainy seasons. 

2. Seed Rot, Black Root Rot, Damping-off — General. Seeds rot. Poor stand. Seed- 
lings and older plants wilt and collapse or survive and produce sickly, yellowish, 
stunted plants. Control: Rotate. Plant in well-drained soil. Treat seed with thiram, 
captan, or dichlone (Table 13 in the Appendix) . If damping-off starts, water 
with captan (li/, tablespoons per gallon; use 1 pint per square foot) . 

3. Curly-top — Common and serious in the western half of the United States. Younger 



BEET 137 

leaves curl upward. May later turn yellow. Plants become stunted or dwarfed with 
thickened, rolled, dull green, crimped, or brittle leaves. Roots are "hairy" or 
"woolly." Black rings appear when beet is cut across. Young plants may turn 
yellow and die. Control: Plant as early as practical or at the time recommended 
for your area. Keep down weeds. Varieties differ in resistance. See also under Bean, 
and (19) Curly-top under General Diseases. 

4. Spinach Fusarium Yellows, Wilt — General. Young plants stunted, or may wilt and 
die. Leaves pale, turn yellow, wilt, and die slowly starting with the oldest leaves. 
Brown streaks inside root. Roots decay. Control: Long rotation. Harvest early. 
Destroy plant debris after harvest. If practical, plant in clean or sterilized soil. 
See "Soil Treatment Methods and Materials" in the Appendix. Resistant varieties 
of spinach offer the best hope (e.g., strains of Virginia Savoy and Domino) . 

5. Blackleg, Crown or Heart Rot, Dry Rot — Dark brown to black cankers at soil 
line or on taproot. Lower leaves turn yellow, then brown, and fall early. Seed- 
lings may darken and collapse. Control: Plant disease-free seed in warm, well- 
drained soil in a well-prepared seedbed. Avoid overcrowding, excessive soil acid- 
ity, and too deep planting of seed. Soil should be adequately supplied with boron. 
Keep plants growing vigorously. 

6. Blackheart (primarily beet) — General. Locally severe where the phosphorus sup- 
ply in the soil is low. Plants often slightly stunted. Leaves dark green with dark 
brown areas between the veins. Leaf edges may be shriveled; spinach leaves may 
be small and curled. Taproot is internally discolored. Control: Have the soil 
tested. Apply the recommended amount of superphosphate-containing fertilizer. 

7. Heart Rot, Boron Deficiency, Cracked Stem — Locally severe where boron is lack- 
ing in the soil. Middle and older leaves are abnormally crinkled. If severe, young 
leaves are stunted, twisted, narrow, and redder or blacker (pale green or yellow 
in spinach) in color than normal. These leaves may wilt and die in midsummer. 
Gray, brown to black, internal or external dry rot of the taproot. See Figure 1. 
Control: Have the soil tested. Apply borax as recommended. Resistant beet vari- 
eties: Detroit Dark Red and Long Blood. 

8. Crown Gall — Occasional. Swollen, gall-like growths near the soil line. See (30) 
Crown Gall under General Diseases. 

9. Mosaics, Savoy, Yellow Net, Yellow Vein, Ringspot — Widespread. Leaves mottled; 
light and dark green or yellow. Leaf surface often crinkled and curled (or sa- 
voyed) . May show faint zigzag lines, rings, and other patterns. Leaves die back 
from the tips. Growth is often stunted. Center leaves are often mottled, stunted, 
and distorted. Beet roots are smaller than normal. May be "hairy." Control: Plant 
virus-free seed from healthy mother plants. Keep down weeds. Destroy the first 
infected plants. Maintain balanced soil fertility. Control aphids and plant bugs, 
which transmit the viruses, by applying malathion weekly. 

10. Virus or Beet Yellows, Spinach Blight (beet, Swiss chard, mangel, mangold, spin- 
ach, New Zealand spinach, summer-cypress) — Symptoms variable depending on the 
plant, virus strain, and other factors. Plants often dwarfed and yellowed. The veins 
in young leaves are usually conspicuously yellow (cleared) . Outer and middle leaves 
gradually become yellow, thickened, and brittle. Yellowing usually starts at the 
upper margins and tips. Table beet leaves are usually deep red with little yellowing. 
Leaves may later turn brown and die prematurely, starting at the tips. Root may be 
small. Yellows-infected plants may be more susceptible to Leaf Spot and other 
diseases. Control: Plant late or early to avoid the summer migration of aphids which 
transmit the viruses. Use virus-free seed. Keep down weeds and wild beets in and 



138 BEET 

around the garden. Many weeds are symptomless carriers. Spray in the spring to 
control aphids using malathion. Plant normally resistant spinach varieties: Blight 
Resistant Virginia Savoy, Dixie Market, Domino, Early Hybrid No. 7, Old Domin- 
ion, and Virginia Blight Resistant. Check the adaptability of spinach varieties with 
your county agent or extension horticulturist. Beet varieties also differ in resistance. 

11. Downy Mildew, Blue Mold — General during cool, humid seasons. Young leaves 
are covered with a violet- or yellowish-gray mold. Older leaves have small to large, 
irregular, pale green or yellow areas on the upper leaf surface with the mold 
growth on the underside. Leaves may become thickened and curled, dry up, 
darken, or rot. Similar spots occur on the seed stalks which may be stunted or 
killed. Serious in cool, wet weather. Damaging to spinach and Swiss chard in the 
seedbed. See Figure 20D under General Diseases. Control: Three-year rotation. 
Avoid overcrowding. Keep down weeds. Plant disease-free seed in well-drained, 
fertile soil. Destroy old crop debris. Spray when disease is first seen, using zineb, 
maneb, chloranil, or a copper-containing fungicide. Repeat at 5- to 10-day inter- 
vals. Soak spinach seed in hot water (122° F.) for 25 minutes. Dry, then dust 
with thiram, chloranil, dichlone, captan, or Semesan. Resistant spinach varieties: 
Badger Savoy, Califlay, Dixie Market, Early Hybrid No. 7, Savoy Supreme, Vi- 
king, and Wisconsin Bloomsdale. Resistant beet: F.M. Detroit Dark Red. 

12. Scab — Widespread. Raised, rough, scablike areas or warts on the root. See under 
Potato. Worst in lime-rich soils. Control: Do not grow in soil which has produced 
scabby potatoes. Keep soil acid. Varieties differ in resistance. 

13. Root Gall, Root-knot, Cyst Nematodes — See under Bean, and (37) Root-knot un- 
der General Diseases. Control: If serious enough, fumigate soil with D-D or Telone 
before planting. 

14. Watery Soft Rot, Drop, Stem Rot, Wilt, Storage Rots — See under Carrot. 

15. Rusts — Western half of the United States. Small, yellow to bright orange, reddish- 
brown, or dark brown pustules, mostly on underside of leaves. Leaves may wither. 
One rust is serious only near the alternate hosts — salt and needle grasses (Distich- 
lis and Aristida) . Control: Spray as for Cercospora Leaf Spot and Downy Mildew 
(both above) or use dichlone. Destroy nearby salt and needle grasses by burning 

in the fall or plowing under deeply. Destroy tops after harvest. 

16. Root Rots, Crown Rots, Southern Blight — General. See under Bean, and (34) 
Root Rot under General Diseases. Beet varieties in the future may have resistance. 

17. White-rust — Southern states. Small, white, powdery pustules mostly on underleaf 
surface. If severe, leaves or entire plants may wither and die. See Figure 23C un- 
der General Diseases. Control: Three-year rotation. Plant disease-free seed. Spray- 
ing as for Downy Mildew and Leaf Spot (above) may be beneficial. Destroy in- 
fected plants and debris after harvest. 

18. Minor Leaf Spots, Anthracnose — General. Small, round to irregular, variously 
colored leaf spots. Spots often enlarge and run together. Leaves may wither and 
die. Mold growth may develop on affected parts in damp weather. Control: Same 
as for Cercospora Leaf Spot (above) . 

19. Web Blight — Southeastern states. See under Bean. 

20. Gray-mold Blight — See (5) Botrytis Blight under General Diseases. 

21. Black Streak, Bacterial Spot (beet) —Western states. Irregular, dark brown to 
black, spots on leaves and streaks on the leaf stalks, midrib, and larger leaf 
veins. Affected leaves may bend over sharply, become limp, and later wither. 
Control: Plant disease-free seed in soil which has not grown beets or related crops 
for at least 3 years. Collect and burn or bury plant debris after harvest. Avoid 
overfertilizing with nitrogen. 



BEGONIA 139 

22. Bacterial Soft Rot — General. See (29) Bacterial Soft Rot under General Dis- 
eases. Control: Same as for Black Streak (above) . 

23. Bacterial Pocket, Beet Gall (garden and sugar beets) — Deeply indented, tumor- 
like growths on crown of roots. Galls have irregular brown areas inside. Galls 
soon disintegrate. Control: Same as for Black Streak (above) . Avoid cultivating 
injuries. 

24. Bacterial Wilt — See (15C) Bacterial Wilt under General Diseases. 

25. White or Leaf Smut (spinach) — Indistinct white spots on the lower leaf surface. 
When severe, leaves may whiten. Control: Not usually necessary. Same as for 
Cercospora Leaf Spot and Downy Mildew (both above) . 

26. Spinach Yellow Dwarf — Young leaves may be mottled light and dark green, 
curled, and puckered. Older leaves develop yellow blotches. Heart leaves are 
stunted. May turn yellow and die. Control: Do not grow spring spinach near win- 
ter spinach. Destroy wild spinach plants. With malathion control aphids which 
transmit the virus. 

27. Spotted Wilt, Ringspot — Zigzag lines or other irregular markings on the leaves. 
See (17) Spotted Wilt under General Diseases. 

28. Chlorosis — Leaves turn yellowish-green or yellow, first at the margins, later be- 
tween the veins. Leaves may later wither and die. This disease is due to a de- 
ficiency of iron or manganese in alkaline soils. Control: Acidify soil or spray 
plants with iron sulfate or manganese sulfate or both, 1 ounce in 2i/2 g a U° ns of 
water. Plants should recover in 1 to 2 weeks. Repeat as necessary. 

29. Other Root-feeding Nematodes (e.g., lance, naccobus, pin, reniform, meadow or 
root-lesion, rot, sheath, spear, spiral, sting, stubby-root, stylet or stunt) — Associ- 
ated with stunted, sickly plants. Roots short, stubby, discolored, and die back. 
Nematodes make wounds for root-rotting fungi. Control: Same as for Root Gall 
(above) . 

30. Verticillium Will (beet, spinach) —See (15B) Verticillium Wilt under General 
Diseases. 

31. Powdery Mildew (beet) —See (7) Powdery Mildew under General Diseases. 

BEGONIA [FIBROUS ROOTED, HARDY, HYBRID, REX or FOLIAGE, 
RHIZOMATOUS, TUBEROUS ROOTED, WAX or EVERLASTING] (Begonia) 

1. Gray-mold Blight, Botrytis Blight, Blotch — Cosmopolitan and serious. Large, 
blotchy, dead areas on leaves, stems, cuttings, and flowers. A coarse gray mold 
grows on affected parts in wet weather. Leaves and flowers turn brownish-black 
and die. Common in greenhouses. Control: Destroy severely affected plants or 
plant parts when first found. Space plants. Improve air circulation. Keep water 
off the foliage. Keep down weeds. Avoid a wet mulch and overwatering. Plant in 
sterilized soil (pages 437-44) . Keep plants growing at a steady rate. Indoors use 
sufficient light. Apply captan, maneb, or zineb to plants and soil. 

2. Crown, Stem and Root Rots, Cutting Rot, Damping-off — Cosmopolitan. Plants 
pale. Cause poor growth. Stems and crowns often water-soaked and darkened 
near the soil line. Often collapse. Lower leaves may be water-soaked and flabby. 
Roots discolored and decayed. Seedlings and cuttings rot. Tubers may also rot. 
May be associated with root-feeding nematodes (e.g., root-lesion or meadow, spiral) . 
Control: Same as for Gray-mold Blight (above) . Use seed and leaves from disease- 
free plants. 

3. Bacterial Leaf Spot, Bacteriosis — Widespread, especially on tuberous begonias. 
Small, round, water-soaked spots which later turn yellow or brown. Spots enlarge 
and run together. Leaves may wither and fall early. Main stem may rot, killing 



140 BELLFLOWER 

plant. See Figure 16B under General Diseases. Control: Same as for Gray-mold 
Blight (above) except use streptomycin when necessary. Propagate with cuttings 
from disease-free plants. Varieties differ in resistance. Indoors reduce the tempera- 
ture and humidity. Keep water off the foliage. Space plants. 

4. Crown Gall — More or less round galls develop on the stem near the soil line. 
Galls may later rot, killing the plant. Control: Take tip cuttings and then destroy 
the mother plant. Pot in sterilized soil (see pages 437-44) . Avoid wounding stems. 
Space plants for good air movement. 

5. Root-knot — See (37) Root-knot under General Diseases. Plants stunted and sickly. 
On tuberous begonias the root galls become quite large. 

6. Powdery Mildews — Common. May be serious on tuberous begonias. White blotches 
on leaves. Leaves often deformed. Control: Apply Kara thane or phaltan, plus a 
spreader-sticker, when mildew is first seen. Repeat as necessary. Acti-dione has also 
proven effective. 

7. Leaf Nematode Blight — Widespread and serious. Small to large, irregular, brown 
patches on leaves between the veins. Leaves curl up and drop off. Plants often 
stunted and unsightly. See (20) Leaf Nematode under General Diseases. Control: 
Keep water off the foliage. Space plants. Propagate only from disease-free plants. 
Plant in sterilized soil. Where necessary, dip or spray plants weekly with malathion. 
Remove and burn all infested plant parts. Begonias in small pots may be disin- 
fested by dipping in hot water (1 minute at 120° to 121° F.; 3 minutes at 
117° to 119° F.; or 5 minutes at 115° F.) . 

8. Spotted Wilt — Zoned, yellowish to brown, or ringlike spots on leaves. Plants 
stunted and bronzed in color. Control: Destroy infected plants. By using DDT con- 
trol thrips which transmit the virus. 

9. Aster Yellows — Plants stunted, bushy, and yellow in color. Control: Same as for 
Spotted Wilt, except virus is spread by leafhoppers. 

10. Corky Scab, Oedema — Indoor plants show small, water-soaked spots which later 
become light brown, corky growths. Found on underside of leaves and along 
stems. Control: Avoid overwatering or sprinkling plants. Keep down humidity 
in cool, cloudy weather. 

11. Leaf Spots, Anthracnose — Spots of various sizes, shapes, and colors on leaves. 
Control: Same as for Gray-mold Blight (above) . 

12. Mosaic — Uncommon. Yellowish areas and sometimes brown spots, between the 
leaf veins. Control: Destroy affected plants. Spray or fumigate to control aphids and 
other insects. Use DDT or methoxychlor and malathion. 

13. Verticillium Wilt — See (15B) Verticillium Wilt under General Diseases. 

BELAMCANDA - See Iris 

BELLADONNA LILY - See Chrysanthemum 

BELLFLOWER [AMERICAN, CHIMNEY, TUSSOCK, WILLOW or PEACH 

BELLS], BLUEBELLS-OF-SCOTAND, CANTERBURY-BELLS, HAREBELL 
(Campanula); BALLOONFLOWER, CHINESE BELLFLOWER (Platycodon); 
VENUS-LOOKINGGLASS (Specularia) 

1. Leaf Spots — Small to large, round to irregular, yellowish, brown, or grayish spots 
on leaves. Control: Destroy tops in the fall. Apply zineb, captan, or a copper-con- 
taining fungicide, several times, 10 days apart. 

2. Stem Rot, Groivn Rot, Southern Blight, Root Rots — Grayish-white, cottony, or 



BIGNONIA 141 

brown areas on stem which later enlarge. Stem rots, causing plant to wilt and 
collapse. Control: Dig up and burn infected plants and surrounding soil. Four- 
to 6-year rotation. Plant in clean or sterilized soil. See "Soil Treatment Methods 
and Materials" in the Appendix. 

3. Rusts (bellflower, venus-lookingglass) —Widespread. Yellow, orange, reddish- 
brown or black, powdery pustules on underside of leaves. Plants stunted. Usually 
serious if certain infected pines (alternate host of one rust) are growing nearby. 
Control: Avoid growing near pines (Pinus rigida and P. resinosa) , or apply zineb, 
ferbam, or maneb, three times, 10 days apart, starting when rust is first seen. 

4. Root-knot — See (37) Root-knot under General Diseases. 

5. Powdery Mildew (bellflower, Canterbury-bells) — See (7) Powdery Mildew under 
General Diseases. 

6. Spotted Wilt (Canterbury-bells) — Plants stunted. Growth is poor. Leaves show 
pale ringspots or wavy line markings. Control: Destroy infected plants. Control 
thrips which transmit the virus. Use DDT or malathion. 

7. Aster Yellows (Canterbury-bells) —See (18) Yellows under General Diseases. 

8. Gray-mold Blight, Crown Rot — See under Begonia, and (5) Botrytis Blight under 
General Diseases. 

9. Verticillium Wilt — Lower leaves turn yellow, wilt, and die. Wilt gradually pro- 
gresses up the plant. Control: Destroy infected plants. Rotate. Plant in well- 
drained soil. 

10. Mosaic — See under African-violet, and (16) Mosaic under General Diseases. 
W.Seed Smut (venus-lookingglass) —Seeds filled with dark, powdery masses. Control: 

Plant disease-free seed. 
12. Leaf and Stem Nematode (bellflower) — See (20) Leaf Nematode under General 

Diseases. 

BELLIS — See Chrysanthemum 

BELLS OF IRELAND -See Salvia 

BELLWORT-See Lily 

BELOPERONE-See Clockvine 

BENINCASA-See Cucumber 

BENT, BENTGRASS - See Lawngrass 

BENZOIN - See Avocado 

BERBERIS-See Barberry 

BERMUDAGRASS —See Lawngrass 

BETONY-See Salvia 

BIDENS — See Chrysanthemum 

BIGNONIA, TRUMPETFLOWER, CROSSVINE, CHINESE TRUMPETCREEPER 

(Bignonia) 

l.Leaf Spots, Spot Anthracnose — Leaves variously spotted. Control: See under 
Chrysanthemum. 



142 BIRCH 

2. Sooty Mold, Black Mildews — Southern states. Black, moldy patches on foliage. 
See (12) Sooty Mold under General Diseases. 

3. Gray-mold B Ugh t — Southern states. See (5) Botrytis Blight under General Dis- 
eases. 

4. Root-knot — See (37) Root-knot under General Diseases. 

5. Dieback, Canker — See under Apple. 

BINDWEED — See Morning-glory 

BIRCH [BLACK, CUTLEAF, DWARF, EUROPEAN, GRAY or POPLAR, 

MONARCH, PAPER or CANOE, PYRAMIDAL, RIVER or RED, SWAMP or 

HAIRY DWARF, SWEET or CHERRY, WATER, WEEPING, WESTERN PAPER, 

WHITE, YELLOW ] (Betula); ALDER [ AMERICAN, BLACK, CUTLEAF BLACK, 

EUROPEAN GREEN, GREEN, HAZEL or SMOOTH, ITALIAN, SPECKLED or 

HOARY-LEAVED, JAPANESE, MANCHURIAN, NEW MEXICAN, SEASIDE, 

SIERRA, SITKA, SPECKLED, THINLEAF, WEEPING] (Alnus); HORNBEAM 

[ AMERICAN, EUROPEAN, HEARTLEAF, YEDDO ] (Carpinus); HAZELNUT 

[ AMERICAN, BEAKED or CUCKOLD, CALIFORNIA, CHINESE, EUROPEAN, 

JAPANESE, TIBETIAN, TURKISH], FILBERT, PURPLE-LEAVED FILBERT 

(Corylus); IRONWOOD, HOPHORNBEAM [AMERICAN, EASTERN, 

EUROPEAN, JAPANESE ] (Ostrya) 

I.Wood Rots, Heart Rots, Butt Rots — Cosmopolitan. Wood may be lightweight, 
soft, and punky. Hoof- or shelf-shaped fruiting bodies (conks) develop along 
dead or dying trunk and branches. Diseased wood may be discolored or stained. 
See Figure 39 under General Diseases. Control: Maintain good tree vigor by ferti- 
lizing and watering during dry periods. Control other diseases and insects. Avoid 
wounding the bark. Paint over all wounds promptly with a good tree wound 
dressing. 

2. Dieback, Twig, Branch and Trunk Can k ers — Upper branches progressively die 
back. Irregular, swollen cankers may develop on twigs, branches and trunk. In- 
fected trunk and branches may be flattened and bent. Plant parts die when 
cankers girdle. Often associated with borers, drought, and other diseases. Control: 
Destroy trees with severe trunk cankers. Prune out and burn young cankers and 
all dead wood. Make clean, flush cuts. Sterilize tools between cuts. Otherwise same 
as for Wood Rots. 

3. Leaf Spots, Anthracnose — Widespread. Round to irregular, brownish, yellowish 
or gray spots, following cool, wet, spring weather. If spots are numerous, leaves may 
drop early. Control: Seldom necessary. Collect and burn fallen leaves. If practical, 
spray as for Leaf Rust (below) or use captan. 

4. Leaf Rust — Numerous, small, bright reddish-yellow, later dark brown to nearly 
black, powdery pustules on the lower surface of leaves. Leaves may drop early. 
Seldom serious. Control: Do not plant near larch, the alternate host of this rust. 
If practical, apply zineb, maneb, or dichlone as the buds burst open. Repeat 10 
and 20 days later. 

5. Leaf Blisters or Curls, Witches' -broom — Yellow or red blisters may cause the 
leaves to be swollen, distorted, curl, and drop early. Hypertrophy of mature fertile 
catkins on alders. Clusters of weak twigs (witches'-brooms) may arise near the same 
spot on the twigs. See (10) Leaf Curl under General Diseases. Control: Prune out 
witches'-brooms. Collect and burn fallen leaves. If practical, apply ferbam or a 
copper-containing fungicide, plus spreader-sticker, once before the buds swell 
in early spring. 



BITTERSWEET 143 



6. Powdery Mildews — Widespread. Powdery, grayish-white mold patches on the 
leaves, young twigs, and female catkins of alders. Severely infected leaves may turn 
yellow, wither, and drop early. Control: If severe and where practical: Apply sul- 
fur or Karathane one or two times, 10 days apart, starting when mildew is first seen. 

7. Bacterial Blight, Bacteriosis (hazelnut, filbert) — Serious on the Pacific Coast. 
Brown to black, round to angular spots on the buds, leaves, and young shoots 
(up to 4 years old) in the spring. Cankers develop on young tree trunks. Often 
kills young trees. Maturing nuts are discolored. Control: See under Walnut. Re- 
sistant filberts: Daviana, Bolwyller, and Graham. Apply bordeaux mixture (3-1 1/2- 
50) in August before fall rains. Repeat when s/ 4 of leaves have dropped. Sterilize 
pruning tools with mercuric chloride or 70 per cent denatured alcohol. 

8. Slime Flux, Wetwood — See under Elm. 

9. Root Rots — Trees decline in vigor. Foliage is thin and sickly. Leaves may turn 
yellow, wither, and drop early. See under Apple, and (34) Root Rot under Gen- 
eral Diseases. 

10. Sooty Mold — See (12) Sooty Mold under General Diseases. 

11. Crown Gall — See under Apple, and (30) Crown Gall under General Diseases. 

12. Kernel Bitter Rot, Brown Stain (hazelnut) — Problem on the Pacific Coast. Check 
with local authorities (see above) . 

13. Root-knot — See under Peach, and (37) Root-knot under General Diseases. 

14. Twig Blights, Dieback, Bark Canker — Widespread. Discolored cankers girdle the 
stems causing the foliage and stems beyond to wither and die. Control: Prune out 
and burn dead and cankered wood. Spraying as for Leaf Rust (above) may be 
beneficial. 

15. Bleeding Canker— Northeastern states. See under Beech and Maple. 

16. Felt Fungus (hornbeam) —Southern states. Smooth, buff-colored growth on the 
bark. See under Hackberry. 

17. Mistletoe — See (39) Mistletoe under General Diseases. 

BIRD-OF-PARADISE-FLOWER (Strelitzia) 

I. Root and Seed Rot — See (34) Root Rot under General Diseases. May be asso- 
ciated with root-feeding nematodes (e.g., burrowing, root-lesion, stubby-root) . 
Control: Plant disease-free seed or soak seed for a day in water (at room tempera- 
ture) then in hot water (135° F.) for 30 minutes. Cool, dry, and plant in clean 
or sterilized soil. 

BIRTHWORT - See Aristolochia 

BISHOPSCAP - See Hydrangea 

BITTERSWEET [CLIMBING, ORIENTAL or CHINESE] (Celastrus); 

ARABIAN-TEA (Catha); EUONYMUS [ BROADLEAF, BROOK or 

STAWBERRY-BUSH, CLIMBING, EVERGREEN or EVERGREEN BURNING-BUSH, 

JAPANESE EVERGREEN, WINTERBERRY, YEDDO], SPINDLE-TREE 

[ALDENHAM, EUROPEAN, WINGED or WINGED BURNING-BUSH], 

BURNING-BUSH or WAHOO, and WINTERCREEPER [ BIGLEAF, GLOSSY, 

SILVER-EDGE] (Euonymus); CLIFFGREEN, MYRTLE BOXLEAF (Pachistima) 

I. Powdery Mildews — Widespread. May be serious. White, powdery mold patches on 
the leaves. Leaves may turn yellow and drop early. Control: Remove badly at- 
tacked shoots. Prune to thin out shrubs. Where practical, apply sulfur, Karathane, 



144 BLACK-ALDER 

or Acti-dione several times, 10 days apart. Avoid applications when the temperature 
is above 85° F. 

2. Crown Gall — Common. Large, irregular galls appear on both the roots and stems. 
Euonymus may be severely infected. See (30) Crown Gall under General Diseases. 

3. Leaf Spots, Anthracnoses, Leaf Scab — Variously sized and colored spots on the 
leaves. Common following wet weather. Control: Collect and burn fallen leaves. 
Prune to thin out shrubs. Apply zineb, maneb, or fixed copper several times, 7 
to 10 days apart. Start as the leaves are unfolding. 

4. Stem Cankers, Dieback — See under Maple. Same as for Leaf Spots (above) . Cut 
out and burn dead and dying twigs. 

5. Root-knot — See (37) Root-knot under General Diseases. 

6. Other Root-feeding Nematodes (e.g., dagger, needle, pin, ring, root-lesion, spiral, 
stylet) — Associated with sickly stunted plants. Control: Same as for Root-knot 
(above) . 

7. Euonymus Mosaic, Infectious Variegation — Yellowing develops along the leaf 
veins. Control: Do not use variegated plants for propagating. If serious enough, 
destroy infected plants. 

8. Thread Blight (euonymus) — Southeastern states. See under Walnut. 

BLACK-ALDER - See Holly 

BLACKBERRY - See Raspberry 

BLACKBERRY-LILY - See Iris 

BLACK COHOSH -See Anemone 

BLACK-EYED-SUSAN - See Chrysanthemum 

BLACK GUM -See Dogwood 

BLACKHAW-See Viburnum 

BLACK-SALSIFY - See Lettuce 

BLACK SAMPSON -See Chrysanthemum 

BLACK-SNAKEROOT - See Anemone 

BLACKTHORN - See Peach 

BLACK WALNUT -See Walnut 

BLADDERNUT— See American Bladdernut 

BLADDER-SENNA -See Honeylocust 

BLAZING-STAR — See Chrysanthemum 

BLECHNUM-See Ferns 

BLEEDINGHEART, DUTCHMANS-BREECHES, SQUIRRELCORN (Dicenfra); 

CORYDALIS 

1. Rusts (Dutchmans-breeches, corydalis) —Yellowish-orange spots on the upper leaf 
surface with clusters of slender, cuplike structures developing on the lower sur- 
face. Alternate hosts include wood-nettle and wild grasses. Control: Destroy nearby 
alternate hosts. If practical, apply zineb, maneb, or ferbam several times, 10 days 
apart, starting when rust is first seen. 

2. Crown Rot, Stem Rots, Wilt — See (21) Crown Rot under General Diseases. 



BLUEBERRY 



145 



3. Fusarium Wilt (bleedingheart) —See (15A) Fusarium Wilt under General Dis- 
eases. 

4. Downy Mildew — May be serious on plants growing in shade. See (6) Downy Mil- 
dew under General Diseases. 

5. Leaf Spot — Small spots on leaves. Control: Spray or dust as for Rusts (above) . 

BLESSEDTHISTLE-See Chrysanthemum 

BLOODROOT — See Poppy 

BLUEBEARD - See Lantana 

BLUEBELL OF ENGLAND -See Tulip 

BLUEBELLS - See Mertensia 

BLUEBERRY [BOX, CLUSTER, DRYLAND, GROUND, HIGHBUSH (BLACK, 

NORTHERN, SOUTHERN or SWAMP), LOWBUSH (RABBITEYE, SUGAR, 

UPLAND, MOUNTAIN CRANBERRY or LINGONBERRY)] (Vaccimum); 

STRAWBERRY-TREE, MADRONE (Arbutus); MANZANITA, BEARBERRY 

(Arctostaphylos); CASSANDRA or LEATHERLEAF (Chamaedaphne); 
CASSIOPE; HUCKLEBERRY [ BLACK, BOX, GARDEN, DANGLEBERRY ] 
(Gayhssacia); BOG LAUREL, MOUNTAIN-LAUREL, PALE LAUREL, SHEEP- 
LAUREL or LAMBKILL (Kalmia); KALMIOPSIS; FETTERBUSH, MALEBERRY, 
STAGGERBUSH (Lyonia); RUSTYLEAF, MINNIE-BUSH (Menziesia) 

I. Mummy Berry, Brown Rot, Blossom Blight, Twig Blight (blueberry, mountain- 
laurel) — General eastern half of United States. Tips of new shoots wilt and turn 



Fig. 78. Mummy berry 
of blueberry. The 5 dark 
berries to the upper left 
are "mummy berries." 
The rest of the fruit is 
healthy. 




146 BLUEBERRY 

brown. Blossoms blasted. Nearly full grown blueberry fruit turn gray or tan, then 
shrivel into hard mummies. See Figure 78. Control: Avoid crowding and over- 
fertilizing plants. Resistant blueberry varieties: Cabot, Stanley, and Weymouth. 
Apply captan, zineb, ziram, ferbam, or dichlone several times, 7 to 10 days apart, 
starting when the buds unfold. Practice very clean cultivation in the spring 
through bloom. 

2. Botrytis Blight, Gray-mold Blight — General. Blossoms blasted. Young blueberry 
fruit shrivel and turn a dull bluish-purple. They soon fall. There are irregular, 
brown leaf blotches. Tips of shoots die back. A gray mold may grow on affected 
parts. Control: Spray as for Mummy Berry (above) . Avoid spring applications of 
fertilizer high in nitrogen. Prune shrubs annually. 

3. Red Leaf Gall, Swamp Cheese, "Rose Bloom," Shoot Hypertrophy — General. Gall- 
like growths on twigs. Small, red blisters on leaves. Blossoms and small fruit swell 
abnormally. Affected parts turn pink to bright red in summer before falling off. 
Control: Plant disease-free stock. Prune and burn infected parts when first seen. 
If necessary, apply a single dormant spray before the buds swell, using copper, 
ferbam, or zineb. 

4. Powdery Mildew — General on blueberry. Compact whitish mold on upper sur- 
face of leaves of certain susceptible varieties (Adams, Concord, Jersey, and Ru- 
bel) . Etched, water-soaked spots appear on the lower surface of young leaves. 
Spots enlarge and the leaves of susceptible varieties (e.g., Pioneer, Cabot, Ware- 
ham) gradually turn yellow and may drop early. Mildew usually occurs after 
harvest and causes little damage. Control: Grow resistant blueberry varieties: 
Harding, Rancocas, Stanley and Weymouth. Apply Kara thane twice, 10 days apart. 

5. Crown Gall — Sometimes called Cane Gall. Swollen, rough, irregular, light brown 
to black galls along stems and small twigs. Sometimes at base of stems. Galls may 
girdle and kill stems. Control: Destroy severely infected plants. Use disease-free 
plants. When only slight infection is found, make pruning cuts several inches be- 
low any sign of infection. Disinfect before each cut by dipping shears in a 1:1,000 
solution of mercuric chloride (see page 85 for precautions) . 

6. W itches' -broom — Short, swollen twigs crowded together giving a bushy or broom- 
like appearance. No fruit produced. Found near firs, the alternate host of the 
rust fungus. Witches'-broom of mountain-laurel is not caused by a rust. Control: 
Prune out and burn infected branches. Spraying as for Mummy Berry and Gray- 
mold Blight (both above) is probably beneficial. Destroy nearby, worthless true firs 
and infected blueberry plants since the rust fungus is perennial and systemic. 

7. Leaf Rust — Widespread. Small, irregular, reddish-brown or black spots and yel- 
lowish pustules on the leaves. Leaves may wither and drop early. Severe only in 
certain years near hemlocks or spruces, the alternate hosts of the rust fungus. 
Control: If practical, spray as for Mummy Berry and Gray-mold Blight (both 
above) . Grow resistant blueberry varieties. 

8. Blueberry Stunt — Symptoms vary with time of year, stage of growth, and variety. 
The tip leaves on young shoots in the spring are first pale yellow at the margins 
and tip. Later the leaves turn completely yellow except for the leaf veins. These 
leaves become round, dwarfed, and cupped. Leaves on old canes turn prematurely 
red in early fall. The brilliant red color occurs in two lengthwise bands on the 
leaf. Plants are stunted and bushy with numerous, dwarfed side twigs. Affected 
plants are unproductive with small, bitter fruit. Leafhoppers transmit the virus. 
Control: Use only certified, virus-free nursery stock. Promptly dig up and destroy 
infected bushes, including the roots, when first found. Destroy wild blueberry 
plants in the area. Follow the spray program in the Appendix. Rancocas and 
Harding are highly resistant varieties. 



BLUEBERRY 147 

9. Blueberry Mosaic — Leaves on one or more canes are brilliantly mottled with 
yellow, yellow-green, and red areas. The lower leaves on a cane generally show 
more color. Fruit production gradually declines. Mosaic is reported commonly 
on Stanley, Concord, and Dixi. Control: Same as for Stunt (above) . 

10. Blueberry Shoestring — Symptoms variable, even on the same plant. Brown to 
red bands develop along the midrib of a leaf and often extend partially into 
the lateral veins. Such leaves are wavy, distorted, and crescent-shaped. Severely 
affected leaves are narrow, pointed, strap-shaped, and light green to dull red in 
color. On certain varieties (e.g., Burlington, Cabot, and Jersey) red streaks, 
bands, or oval patches occur along the new canes and twigs. Cane growth is long 
and spindly. Such canes do not produce fruit. Control: Same as for Stunt (above) . 

11. Blueberry Ringspots — Eastern states. Leaves develop conspicuous, yellow to dead 
or red rings, spots, line, or jagged oakleaf patterns. Rings may drop out giving a 
tattered appearance. Rings may be evident on the stems throughout the year. The 
virus spreads rather rapidly in the field. Plants may be stunted and unproductive. 
Twigs die back. Control: Same as for Stunt (above) . 

12. Twig Blight, Cane Cankers — Often follows winter injury, sunscald, excessive soil 
moisture, insect attack, and other factors. Infected shoots wilt, wither, and die due 
to discolored, girdling cankers on the twigs and branches. Control: Remove and 
burn weak, unthrifty plants. Prune and burn blighted twigs in the winter. Make 
clean cuts 6 to 8 inches behind any sign of infection. Spray as for Mummy Berry 
and Botrytis Blight (both above) . Increase vigor by fertilizing and watering during 
summer droughts. Plant disease-free stock of resistant varieties, if available. Check 
with your local nurseryman or extension plant pathologist. 

13. Chlorosis — General in neutral and alkaline soils where these plants are not 
adapted. Leaves turn yellow except for the veins. See Figure 79. Plants are stunted, 
may die. Control: See under Rhododendron. 

14. Wood Rots, Trunk Canker — General. See under Birch, and (23) Wood Rot un- 
der General Diseases. 

15. Root Rots — See under Apple, and (34) Root Rot under General Diseases. 

16. Mistletoe (manzanita) —See (39) Mistletoe under General Diseases. 

17. Leaf Spots, Leaf Blotch, Spot Anthracnose, Anthracnose, Tar Spot — Widespread. 
Small to large, round to irregular spots of various colors on leaves. See Figure 
80. Widespread in rainy seasons. If severe, leaves may wither and drop early. 
Tips of twigs may also be spotted and later blighted. Control: If practical, spray 
as for Mummy Berry (above) . See also Table 10 in the Appendix. For only a 
few plants, pick off and burn infected leaves. Avoid crowding plants. 

18. Bacterial Stem Canker of Blueberry — Serious on the Pacific Coast. Water-soaked 
areas develop on last year's canes during the winter. Infected areas soon turn 
into well-defined, reddish-brown to black cankers. All buds are killed. Stems may 
be girdled and killed. Young plants may die. Control: Grow resistant varieties such 
as Burlington, June, Pioneer, Rancocas, Rubel and Weymouth. Apply bordeaux 

(4-4-50) twice in October and November. 

19. Drought and Winter Injury (mountain-laurel) —Leaves gradually turn brown, 
starting at the tip or margins. Such leaves dry up and later drop off. Control: 
Plant in shady, protected locations. Water plants during dry periods in summer 
and fall. Mulch plants in early winter after ground is frozen. Protect exposed 
plants against winter winds by putting up burlap or canvas barriers. 

20. Black Mildew — Primarily in the Gulf states. See (12) Sooty Mold under General 
Diseases. 

21. Fruit Rots (blueberry) —Fruits rot on plant or after harvest. May be covered 



148 BLUEBERRY 




Fig. 79. Iron chlorosis of mountain-laurel 



Fig. 80. A. Leaf blight (Phcmopsis), and B. 
Leaf spot (Phyllosticta) of mountain-laurel. 



with a gray, brown, or black mold growth. Control: Same as for Mummy Bern' 
(above) . 

22. Blueberry Root Gall — Galls on roots are white at first, later become dark brown, 
woody, and covered with bark. Stem cankers occur near the soil line. Small galls 
may occur on the twigs. Control: Plant resistant varieties such as Dixi, Jersey, 
and Rubel. 

23. Blueberry Red Leaf Disease — Northeastern states on lowbush blueberry. Red 
leaves appear on certain branches with a white, feltlike layer on the undersurface. 
Some infected shoots die back each year. Fruit set is reduced. The causal fungus is 
related to those causing Red Leaf Gall, except that Red Leaf is systemic with 
the fungus, being perennial in the rhizome. Control: Dig out and destroy in- 
fected plants when first found. 

24. Bud-proliferating Gall — Galls form at the soil line. Buds abort to form clusters 
of weak shoots, 1 to 6 inches tall. Control: Same as for Crown Gall (above) . 

25. Root-feeding Nematodes (awl, dagger, lance, pin, ring, root-knot, root-lesion, 
sheath, spear, sphaeronema. spiral, stubby-root, stylet or stunt) — Associated with 



BOUVARDIA 149 

sickly, stunted, declining plants. Control: See (37) Root-knot under General Dis- 
eases. 

BLOODLEAF - See Cockscomb 

BLUEBEARD -See Lantana 

BLUEBELLS-OF-SCOTLAND - See Bellflower 

BLUE BONNET -See Pea 

BLUE COHOSH - See Barberry 

BLUE DAISY — See Chrysanthemum 

BLUE DICKS -See Brodiaea 

BLUE-EYED GRASS -See Iris 

BLUE-EYED-MARY - See Snapdragon 

BLUE GILIA-See Phlox 

BLUEGRASS -See Lawngrass 

BLUE LACEFLOWER - See Celery 

BLUELIPS — See Snapdragon 

BLUE MIST SPIREA-See Lantana 

BLUETS — See Buttonbush 

BOG LAUREL -See Blueberry 

BOISDUVALIA - See Fuchsia 

BOLTONIA, BONESET-See Chrysanthemum 

BORAGE (Borago) — See Mertensia 

BOSTON IVY -See Grape 

BOUGAINVILLEA 

l.Leaf Spot — Leaves spotted during rainy seasons. Control: Collect and burn fallen 
leaves in autumn. If needed, spray several times during rainy periods using zineb 
or maneb. 

2. Mosaic — See (16) Mosaic under General Diseases. 

BOUSSINGAULTIA - See Lythrum 

BOUVARDIA 

1. Rust — Southern states. Yellow, yellowish-orange or dark, powdery pustules on 
leaves. May cause some injury. Control: Pick off and burn spotted leaves. If prac- 
tical, spray several times, 10 days apart, starting 2 weeks before rust normally 
appears. Use ferbam, zineb, or maneb. Indoors keep water off the foliage and 
space plants. 

2. Leaf Nematode — Leaves develop dark, unsightly blotches. Flower clusters are 
deformed and stunted. See (20) Leaf Nematode under General Diseases. 

3. Root-knot — Plants may be stunted and sickly with galls or knots on the roots. 
See (37) Root-knot under General Diseases. 



150 



BOWSTRING HEMP 



BOWSTRING HEMP -See Sansevieria 

BOXELDER-See Maple 

BOX MYRTLE, BOX SANDMYRTLE - See Labrador-tea 

BOXWOOD [ BOX, DWARF or ENGLISH, EDGING, JAPANESE, KOREAN, 

LITTLELEAF, MYRTLE-LEAF, ROSEMARY-LEAF, TREE or AMERICAN, 

VARIEGATED] (Buxus) 

1. Cankers, Diebacks, Twig Blight — General and destructive. Infected branches often 
start growth later in the spring than normal ones. Leaves on such branches curl 
upward close to the stem and turn light green and finally straw-colored. Often 
follows winter injury. Twigs, branches, or main stems die back. Small, pinkish 
to black mounds often develop on affected parts. Control: Before growth starts 
in the spring, remove and burn all leaves on the ground and those lodged in 
twig crotches. Prune out dead twigs and branches as soon as noticeable. Cut out 
cankers on larger branches. Spray: (1) just after removing dead leaves and 
branches and before growth starts, (2) as new leaves are breaking out of the 
buds, (3) 2 and 4 weeks later. Use bordeaux (3-3-50) , lime-sulfur (5 level table- 
spoons per gallon of water) , fixed copper, ziram, ferbam, or phenyl mercury. Pro- 
tect plants against Winter Injury (below) . Maintain vigor by fertilizing and 
watering during droughts. 

2. Leaf Spots, Leaf or Tip Blights, Leaf Cast — Leaves variously spotted. Leaves may 





Fig. 81. Macrophoma leaf spot of box- 
wood. 



become straw-colored, sometimes tan or brown, starting at the margins and tips. 
Conspicuous black dots may be evident on the upper leaf surface. See Figure 81. 
Control: Same as for Cankers (above) . Protect plants against Winter Injury. See 
below. 
3. Winter Injury, Sunscald, Windburn — Serious in northern states. Symptoms vari- 
able. Leaves may turn bronze-colored to rusty-brown or red with dead areas 
around the margin. Leaves dry in late spring. Leaves, twigs, even entire plants 
may die back. Injured bark may be split and peel. Stems are girdled, with the 
parts beyond later dying. Control: Erect burlap or canvas windbreaks to ward off 
drying winter winds and sun. Try spraying with Wilt-Pruf or a similar material 
in late fall. Fertilize in late fall or very early spring. Water plants thoroughly late 
in a dry fall just before the ground freezes. Then mulch plants liberally to prevent 
deep freezing. Check with your local nurseryman or extension horticulturist re- 
garding mulching. In the spring, prune back dead branches to healthy wood. 



BROWALLIA 151 



4. Root Rots — Foliage sickly. Plants may wilt and die suddenly or gradually. Usually 
associated with nematodes. See under Apple, and (34) Root Rot under General 
Diseases. 

5. Nematodes (burrowing, dagger, lance, needle, pin, ring, root-knot, root-lesion or 
meadow, sheath, spiral, stem, sting, stubby-root, stylet or stunt) — Plants weak, 
stunted, lack vigor. May wilt on hot, dry days. Leaves may be a sickly bronze to 
orange color. Plants gradually decline. Branches may die back. Roots stunted, often 
bushy, and dark. Root rot may follow nematode injury. Control: Drench soil 
around plant roots with Nemagon, Fumazone, or VC-13. See "Soil Treatment 
Methods and Materials" in the Appendix. Check also with your nurseryman, ex- 
tension plant pathologist, or entomologist. Mulch, water, and fertilize to keep 
plants as vigorous as possible. Fumigate the planting site before replanting box- 
wood in infested soil. Young, bare-root plants may be disinfested of Root-knot 
(and possibly other nematodes) by dipping in hot water (118° F. for 30 minutes), 
then planting in clean or fumigated soil. 

6. Heart Rots, Trunk Rot — See Wood Rot under Birch, and (23) Wood Rot under 
General Diseases. 

7. Thread Blight — Southeastern states. See under Fig. 

BOYSENBERRY - See Raspberry 

BRACHYCOME - See Chrysanthemum 

BRASSICA-See Cabbage 

BRIDAL WREATH - See Spirea 

BROCCOLI - See Cabbage 

BRODIAEA, TRIPLET LILY, BLUE DICKS, PRETTY-FACE, 
CALIFORNIA-HYACINTH (Brodiaea) 

1. R usts — Western states. Yellow, orange, reddish-brown or black, powdery pustules 
on leaves. Alternate host: none or wild grasses (Agropyron and Elymus). Control: 
Where serious enough, collect and burn rusted leaves after flowering. Apply zineb, 
maneb, or ferbam several times, 10 days apart. Start about 2 weeks before rust 
normally appears. 

BROOM [PORTUGUESE, PURPLE, SCOTCH, SPIKE, WARMINSTER], DYER'S 

GREENWEED, DOUBLE-FLOWERED DYER'S GREENWEED, WOODWAXEN 

(Cytisus, Genista); BUNDLEFLOWER (Desmanthus) 

1. Leaf Spot, Blight, Diebacks — Small, irregular black spots on leaves. Spots enlarge 
rapidly forming a blotch or blight. Leaves drop early. Brown spots may develop 
on the stems. Shoots die back. Plants are often killed in 2 weeks. Control: Destroy 
infected plant parts. Spray weekly, starting when disease is first noticed, using 
bordeaux mixture or fixed copper and spray lime. 

2. Powdery Mildew — Powdery, white mold patches on leaves. Control: Dust or spray 
twice, 10 days apart, using sulfur or Karathane. 

3. Rust — See (8) Rust under General Diseases. 

4. Root Rot — See under Apple, and (34) Root Rot under General Diseases. May 
be associated with root-lesion or meadow nematodes. 

BROUSSONETIA - See Fig 
BROWALLIA - See Tomato 



152 



BROWN-EYED-SUSAN 



BROWN-EYED-SUSAN -See Chrysanthemum 

BRUSSELS SPROUTS -See Cabbage 

BRYONOPSIS - See Cucumber 

BRYOPHYLLUM - See Sedum 

BUCHLOE — See Lawngrass 

BUCKEYE - See Horsechestnut 

BUCKTHORN [ALDER, CALIFORNIA or COFFEEBERRY, CAROLINA (YELLOW 

or INDIAN CHERRY), CASCARA, COMMON, DAHURIAN, GLOSSY, 

HOLLYLEAF or RED-BERRIED] (Rhamnus) 

1. Leaf Spo ts — Widespread, but not destructive. Small, round to elongated, gray, 
brown, or black spots on leaves. Control: Usually not necessary. If needed, apply 
sprays at 10-day intervals during rainy periods. Use zineb, ferbam, or maneb. 

2. Rusts — Widespread. Small, yellow to orange spots on leaves. Causes little damage. 
The rusts spread to nearby oats and grasses where they cause the destructive 
Crown Rust disease. See Figure 82. Buckthorn is a noxious weed in Iowa. In Cali- 




Fig. 82. Crown rust on buckthorn (ex- 
treme closeup). Note aecial "cluster cups." 
(Courtesy Dr. W. H. Bragonier) 



fornia one rust produces black pustules on coffeeberry and hollyleaf buckthorn. 

3. Wood Rots — See under Birch, and (23) Wood Rot under General Diseases. 

4. Powdery Mildew — See (7) Powdery Mildew under General Diseases. 

5. Sooty Mold — Black, powdery mold patches on leaves following aphids or scales. 
Control: Apply malathion to control insects. 

6. Root Rot — See (34) Root Rot under General Diseases. 



BUTTERFLY-PEA 153 

BUCKWHEAT-TREE (Cliftonia); SOUTHERN LEATHERWOOD (Cyrilla) 

1. Leaf Spots — Spots of various sizes, shapes, and colors on leaves. Control: If serious 
enough, collect and burn fallen leaves. Spray during moist periods, using zineb, 
maneb, or ferbam. 

2. Rust (southern leatherwood) — Southeastern states. See (8) Rust under General 
Diseases. Control: Same as for Leaf Spots. 

3. Black Mildew — See (12) Sooty Mold under General Diseases. 

4. Brown Felt Canker — See under Hackberry. 

BUDDLEIA - See Butterflybush 

BUFFALOBERRY - See Russian-olive 

BUFFALOGRASS - See Lawngrass 

BUGBANE — See Anemone 

BUGLEWEED - See Ajuga 

BUNCHBERRY - See Dogwood 

BUNDLEFLOWER - See Broom 

BUNYA-BUNYA - See Araucaria 

BUR-MARIGOLD — See Chrysanthemum 

BURNET -See Rose 

BURNING-BUSH - See Bittersweet and Beet 

BUSH-MALLOW - See Hollyhock 

BUSH MORNING-GLORY - See Morning-Glory 

BUSH-PEA -See Pea 

BUTTER-AND-EGGS - See Snapdragon 

BUTTERCUP - See Delphinium 

BUTTERFLYBUSH [FOUNTAIN, JAPANESE, ORANGE-EYE BUTTERFLYBUSH 

or SUMMER-LILAC] (Buddleia); YELLOW-JESSAMINE, 

CAROLINA JESSAMINE (Gelsemium) 

I.Mosaic (butterflybush) —Leaves mottled light and dark green, malformed, and 
tapered. See (16) Mosaic under General Diseases. 

2. Twig and Stem Canker — See (22) Stem Canker under General Diseases. 

3. Root-knot — Butterflybush is very susceptible. See (37) Root-knot under General 
Diseases. 

4. Sooty Mold, Black Mildew, Leaf Spot — See (1) Fungus Leaf Spot, and (12) Sooty 
Mold under General Diseases. 

5. Root Rot — See under Apple, and (34) Root Rot under General Diseases. 

6. Silky Thread Blight (Carolina jessamine) —Southeastern states. See under Walnut. 

BUTTERFLY-FLOWER - See Tomato 
BUTTERFLY-PEA - See Pea 



154 BUTTERFLYWEED 

BUTTERFLYWEED (Asclepias); PHILIBERTIA 

1. Leaf Spots — Spots of various sizes, colors, and shapes on leaves. Control: See under 
Chrysanthemum. 

2. Rusts — Widespread. Yellow, yellowish-orange, reddish-brown or black, powdery 
pustules on leaves. Alternate hosts: Grama (Bouteloua spp.) , cord grasses {Spar- 
Una), unknown, or none. Control: Pick off and burn rusted leaves. If practical, 
spray with ferbam or zineb, several times, 10 days apart. Start a week or more be- 
fore rust normally appears. 

3. Mosaic (butterflyweed) — Plants dwarfed with stunted, mottled, distorted leaves. 
Irregular, yellowish-green blotches on leaves. Control: Destroy infected plants when 
first found. Control aphids which transmit the virus. Use malathion or lindane. 

4. Root Rot — See under Geranium, and (34) Root Rot under General Diseases. 

5. Powdery Mildew (philibertia) — Powdery, whitish mold on leaves. Control: If 
needed, apply Karathane or sulfur twice, 10 days apart. Start when mildew is first 
evident. 

BUTTERNUT -See Walnut 

BUTTONBUSH (Cephalanthus); CHINCHONA; BEDSTRAW (Galium): BLUETS 
(Houstonia); PARTRIDGEBERRY (Mitchella); JUNGLEFLAME (Ixora) 

l.Leaf Spots, Leaf Blight — Spots of various sizes, shapes, and colors on leaves. Con- 
trol: Pick off and burn affected leaves. If serious enough, apply zineb, maneb, fer- 
bam, or fixed copper during wet periods. 

2. Powdery Mildews (bedstraw, buttonbush) — Widespread. See (7) Powdery Mil- 
dew under General Diseases. Control: Apply sulfur twice, 10 days apart. 

3. Rusts (bedstraw, buttonbush, houstonia) — See under Bellflower, and (&) Rust 
under General Diseases. Alternate hosts: none or Spartina, Distichlis, Aristida, or 
Sisyrinchium. 

4. Downy Mildews (bedstraw, houstonia) — Uncommon. See (6) Downy Mildew un- 
der General Diseases. 

5. Root-knot — See (37) Root-knot under General Diseases. 

6. Black Mildew (partridgeberry) —Unsightly black blotches on foliage. Control: 
Same as for Leaf Spots (above) . Apply malathion to control insects. 

7. Root Rot — See under Apple, and (34) Root Rot under General Diseases. Sickly, 
declining plants may be infested with nematodes (e.g., burrowing) . 

8. Thread Blight — Southeastern states. See under Walnut. 

9. Stem Rot (partridgeberry) —See (21) Crown Rot under General Diseases. 

BUTTON SNAKEROOT - See Chrysanthemum 

BUTTONWOOD - See Sycamore 

BUXUS-See Boxwood 

CABBAGE, BROCCOLI, BRUSSELS SPROUTS, CAULIFLOWER, CHINESE 

CABBAGE or PE-TSAI and PAK-CHOI, KALE, FLOWERING KALE, 

KOHLRABI, MUSTARD [BLACK, LEAF, WHITE], RAPE, RUTABAGA, TURNIP 

(Brassica); STONECRESS (Aethionema); ALYSSUM, YELLOWTUFT, 



CABBAGE 155 

GOLDENTUFT, GOLDDUST (Alyssum); ROCKCRESS, WALLCRESS (Arabis); 

HORSERADISH (Armoracia); PURPLE ROCKCRESS (Aubretia); WALLFLOWER 

(Cheiranthus); SCURVYWEED (Cochlearia); SEAKALE (Crambe); TOOTHWORT 

(Dentaria); WHITLOWGRASS (Dmba); ERYSIMUM, WALLFLOWER [ALPINE, 

SIBERIAN, WESTERN, PRAIRIE ROCKET] (Erysimum); DAMESROCKET, 

ROCKET (Hesperis); CANDYTUFT (Iberis); GARDEN CRESS, PEPPERGRASS 

(Lepidium); SWEET ALYSSUM (Lobularia); HONESTY (Lunaria); STOCK 

[COMMON or TEN-WEEKS, EVENING- or NIGHT-SCENTED] 

(Matthiola); WATERCRESS (Nasturtium or Rorippa); RADISH 

(Raphanus); SMELOWSKIA; DESERTPLUME (Stanleya) 

1. Yellows, Fusarium Wilt — General. Leaves turn a dull yellow, curl, die, and fall 
starting at the base of the plant. May show one-sided growth. Plants sickly and 
stunted. Brown streaks inside stems. Seedlings yellow, wilt, and die. Most serious 
at high soil temperatures. Often mistaken for Black Rot. See Figure 29B under 
General Diseases. Control: Start disease-free seed in disease-free soil. Seed may be 
disinfected by treating in hot water (see under Blackleg below) . Plant resistant 
varieties, where adapted: Cabbage — All-head Select, Badger Ballhead Y.R., Badger 
Market, Badger Shipper, Bugner, Charleston Wakefield, Empire Danish, Globe 
Y.R., Glory 61, Greenback Y.R., Improved Wisconsin All Seasons, Improved Wis- 
consin Ballhead, Jersey Queen, Marion Market, Market Master, Racine Market, 
Red Hollander, Red Yellows Resistant, Resistant Flat Dutch, Resistant Danish, 
Resistant Detroit, Resistant Glory, Resistant Golden Acre, Wisconsin Copenhagen, 
Wisconsin Golden Acre, Wisconsin Greenback Y.R., Wisconsin Pride, and many 
more; Cauliflower — Early Snowball; Brocco li — Calabrese, Di Cicco, Early Green 
Sprouting. Grand Central, Midway, and Waltham 29; Kale — Siberian Kale; Radish 
— Red Prince. 

2. Blackleg, Canker, Dry Rot — General east of the Rocky Mountains. Light brown 
or gray spots on stems, leaves, and seed stalks in which black dots develop. Leaves 



Fig. 83. Blackleg of cabbage. The black 
dots are fungus (Phoma) fruiting bodies. 





may wilt, discolor, and die. Stem is girdled, blackens, and rots. Plants often stunted. 
May break over as head enlarges. Taproot often decays. See Figure 83. Control: 
Collect and burn tops after harvest. Avoid overcrowding plants. Plant in well- 
drained soil. Three-year rotation. Keep down cruciferous weeds. Plant disease- 
free, western-grown seed. If disease has been a problem in the past, soak untreated 



156 CABBAGE 

cabbage and Brussels sprouts seed in hot water (exactly 122° F. for 25 minutes) . 
For cauliflower, collards, broccoli, kale, kohlrabi, rutabaga, and turnip seed, soak 
at the same temperature, but for 20 minutes. For radish, cress, and mustard seed 
soak only 15 minutes. Soak stock seed at 130° F. for 10 minutes. Then dry the 
seed carefully at room temperature and dust with thiram, captan, chloranil, or 
Semesan before planting. See Table 13 in the Appendix. Control cutworms and 
cabbage maggots by spraying a 10-inch strip of soil over the row immediately after 
planting or transplanting. Repeat 10 days later. Use aldrin or chlordane. Control 
other insects using DDT and malathion. Check with your county agent or extension 
entomologist for the latest insect recommendations. Treat seedbed as for Wire- 
stem (below) . 

3. Black Rot, Bacterial Wilt, or Blight — General in warm, moist seasons. Seedlings 
yellow, wilt, and collapse. V-shaped, yellow, brown, or dark green areas with black- 
ened veins usually starting at the leaf margin. Lower leaves of cauliflower and 
stock turn yellow or brown and drop early. One-sided growth is common. Plants 
and flowers are dwarfed. May rot quickly. Black ring inside stem when cut 
across. Control: Same as for Blackleg (above) . Maintain balanced soil fertility. 
Cabbage varieties differ in resistance. Resistant mustard: Florida Broadleaf. Re- 
sistant kale: Dwarf Siberian. 

4. Wirestem, Seed Rot, Damping-off, Collar Rot, Rhizoctonia Disease — General. Seeds 
rot. Seedlings wilt, curl, and collapse from rot at the soil line. Older stems are 
girdled by brown or black cankers, shrivel, turn dark and woody {wirestem) . 
Transplanted seedlings make slow growth or die. Most serious under cool, wet 
conditions. Dark, firm rot of base of cabbage head. Outer leaves wilt, darken at 
base. See (21) Crown Rot, and (22) Stem Blight under General Diseases. Control: 
Same as for Blackleg (above) . If needed, dust seed of radish, cress, and mustard 
with thiram or Semesan. Avoid overcrowding, overfertilizing with nitrogen, and 
overwatering plants. Apply one of the following treatments to soil or around the 
base of young plants: (a) a soil drench of Terraclor 75 (PCNB) and captan 50 
(sold as Terracap and Orthocide Soil Treater "X") , i/ 2 tablespoon of each per 

gallon, applied over 20 square feet just after planting, (b) spread i/ 2 cup each 
of Terraclor 20 and captan 7]/ 2 per cent dust uniformly over 50 square feet and 
rake or rototill evenly into the top 3 inches of soil before planting, (c) apply ziram 
or chloranil sprays in the seedbed at 3- to 7-day intervals to wet both seedlings and 
soil, or (d) treating soil with Vapam or Mylone 3-4 weeks before seeding controls 
diseases, weeds, and nematodes. 

5. Clubroot — General. Yellowish, sickly leaves which wilt on hot days. Plants stunted. 
May die before maturing. Often fail to produce decent heads. Roots greatly en- 
larged and distorted with warty overgrowths or "clubs." See Figure 48 under 
General Diseases and Figure 84. Control: See (35) Clubroot under General Dis- 
eases. In addition, locate the seedbed or flower bed in an area where no infested 
soil can be washed. The seedbed soil should be clean or pasteurized (pages 437-44) . 
Apply Terraclor 75 per cent in the transplanting water using 1 ounce per gal- 
lon. Drench flower bed areas. Apply 2>/ A pint per plant. In furrow drenches of 
Vapam or V.P.M., (1 pint to 100 feet of row) 2 to 3 weeks before planting, give 
excellent Clubroot and weed control. Follow the manufacturer's directions. Plant 
resistant varieties where adapted; for example, stock turnip: Bruce, Dale's Hybrid, 
and May; Rutabagas: Immuna II, Resistant Baugholm, and Wilhemsburger; some 
varieties of stock and wallflower are also resistant. Radish is usually resistant. Re- 
sistant cabbage varieties may be available soon. Keep down weeds in the mustard 
family. 



CABBAGE 



157 





Fig. 84. Clubroot of turnip. 



Fig. 85. Bacterial soft rot of cabbage. 



6. Downy Mildew — General in cool, wet areas. Seedling leaves appear moldy. Pale 
green to yellow spotting of the upper leaf surface of older leaves, followed by 
purpling, browning, wilting, and dying of these leaves. A white or gray mold growth 
forms on the corresponding undersurface of affected leaves. Spots also form on 
heads, stems, flower stalks, and flowers. Spots on the heads or curds are black. 
Young plants may blacken and die. Irregular, brown or black areas may form in 
fleshy turnip or radish roots. Control: Treat seed as for Blackleg (above) . Main- 
tain balanced soil fertility. Avoid overcrowding and sprinkling the foliage. Ro- 
tate. Plant in well-drained soil. Pick off and burn infected plant parts, as they 
appear. In the seedbed or in the field, during cool, rainy periods, apply chloranil, 
maneb or zineb at 5-day intervals. Certain strains of broccoli, cauliflower, Chinese 
cabbage, kale, mustard, radish, rutabaga, and turnip are resistant. 

1. Bacterial Soft Rot, Stump Rot — Cosmopolitan. Slimy, soft head, stem, and root 
rot with a foul odor. Head falls away easily leaving a slimy stump. Often follows 
other diseases, insects (worms and maggots) , or freezing injury. See Figure 85. 
Control: Store only dry, sound heads just above freezing. Collect and burn, com- 
post, or bury plant debris after harvest. Control insects and other diseases. See 
under Blackleg (above) . Avoid injuries while cultivating or harvesting. Soak 
bedding roots of horseradish in a 1:1,000 solution of mercuric chloride for 20 
minutes. See Table 13 in the Appendix. Chinese cabbage varieties differ in re- 
sistance. 

8. Head and Fleshy Root Rots — Primarily a storage problem. See under Carrot. 

9. Leaf Spots, Black Leaf Spot, Anthracnose — General. Pale yellow or white, tan, 
gray, brown, dark green, or black spots on the leaves, petioles, stalks, and seed 
pods. Leaves may wilt, shrivel, and die early. Seedlings may be killed. Cauliflower 
and broccoli heads are discolored. Common in the seedbed, in the field, and in 
storage. Control: Same as for Blackleg (above) . In addition, avoid injuring heads. 



158 CABBAGE 

Refrigerate heads promptly after harvest. Spray in the seedbed as for Downy 
Mildew (above) . In the garden, where practical, apply zineb, ziram, maneb, or 
chloranil several times, 7 to 10 days apart, during rainy periods. Southern Curled 
Giant mustard is highly resistant to Anthracnose. 

10. Bacterial Leaf Spots, Pepper Spot (primarily horseradish, radish, turnip, cauli- 
flower, cabbage, broccoli, Chinese cabbage) —Widespread. Small, dark green, 
brown to purplish, water-soaked (or tan to white) spots on the leaves between 
the veins. Spots later enlarge, dry out and become dark and angular. Dark spots 
may also occur on the petioles and stems. Leaves may wither and drop early. 
Control: Same as for Blackleg (above) . Apply fixed copper or streptomycin sev- 
eral times, 10 days apart, starting when spots are first evident. 

11. White Mold or Blight, Drop, Cottony Rot, Watery Soft Rot, Southern Blight - 
General. Water-soaked areas on the stem and lower leaves. Leaves later wilt, often 
drop. Plant collapses. Cottony mold growth on stem and head. Head may become 
a wet, slimy mass. Roots may decay. Control: Same as for Wirestem (above) . Dig up 
and burn infected plants plus 6 inches of surrounding soil. In addition, store 
only dry, sound heads. Handle carefully. If practical, pick off and burn fading 
flowers. Varieties differ in resistance. 

12. Root-knot, Cyst Nematodes — Similar to Clubroot (above) but galls on roots are 
smaller and usually more evenly distributed. Plants sickly and stunted. Control: 
See under Bean, and (37) Root-knot under General Diseases. 

13. Tipbum — Primarily a problem of cabbage and cauliflower. Tips and margins of 
leaves turn pale, brown, or black and shrivel. If severe, outer leaves may die and 
the tips of the younger and inner leaves are scorched and "papery." Plants usually 
stunted. Head is flabby and weak. Control: Maintain balanced soil fertility (es- 
pecially the ratio of phosphorus and potash) based on a soil test. Early and 
kraut cabbage varieties are normally somewhat resistant (e.g., Wisconsin Copen- 
hagen, Bonanza, Resistant Detroit, and Wisconsin Golden Acre) . Danish types are 
commonly affected. 

14. White-rust, White Blister — Widespread in cool, wet weather. Pale yellow spots 
on the upper leaf surface with white, powdery, blister-like pustules on the under- 
side of leaves, smaller stems, seed pods, and flower parts. Affected parts may be 
swollen and distorted. Plants may be stunted. See figures 23A, B, and D under 
General Diseases. Control: Destroy infected plant parts when seen. Destroy plant 
debris after harvest. Keep down weeds. Long rotation with plants outside the cab- 
bage or mustard family. Where serious, apply chloranil or fixed copper several 
times, 7 to 10 days apart, starting before White-rust normally appears. Try soak- 
ing horseradish roots in hot water (111° F.) for 10 to 15 minutes. Strains of Bo- 
hemian horseradish are resistant. 

15. Boron Deficiency, Brown Heart or Rot — Primarily a problem of broccoli, cauli- 
flower, cabbage, radish, rutabaga, and turnip in alkaline soils. Leaves are often 
mottled or scorched at the edges. May roll, become very brittle and deformed. 
Plants may be dwarfed with very narrow leaves. Stems (stalks) may be hollow 
and edible roots are often "glassy," gray, brown, or black inside. Cauliflower 
curd gradually turns brown. Affected heads are bitter and tough. Control: Have 
the soil tested. Apply borax as recommended. Avoid overliming. Fairly resistant 
cabbage varieties: All-head Select, Wisconsin All Seasons, Wisconsin Ballhead, 
and Wisconsin Hollander No. 8. 

16. Gray-mold Blight, Botrytis B Ugh t — Water-soaked, grayish-green to brownish spots 
and rotting of outer leaves and stem. Young plants may wilt and die. Flowers 
may be spotted and rotted. Affected areas may be covered with a coarse gray mold. 



CABBAGE 



159 



Serious storage problem. Control: Same as for Bacterial Soft Rot (above) . Space 
plants. Avoid overwatering. If practical, spray as for Downy Mildew (above) . In- 
doors, keep down the humidity and increase the air circulation. 
17 '. Mosaics, Flower Breaking — Symptoms variable. May be masked in hot weather. 
Leaves usually more yellow than normal. May drop prematurely. Often distorted, 
mottled, light and dark green or yellow, and crinkled. Cabbage leaves often show 
black flecks or spots (stippling) . Plants may be stunted and bunchy. Stock, dames- 
rocket, sweet alyssum, and wallflower flowers may show blotches or streaks. White 
and yellow stock varieties do not show flower breaking. See Figure 86. Control: 
Destroy affected plants when first found. Keep down weeds (especially wild mus- 
tards, charlock, shepherds-purse, yellow-rocket, and pennycress) in and around the 
seedbed and garden area. Resistant or tolerant cabbage varieties include Badger 
Ballhead Y. R., Badger Market, Empire Danish, Improved Wisconsin Ballhead, 



DISEASED 




Fig. 86. Mosaic or flower breaking of 
stock. A. Healthy, B. Diseased. 



Fig. 87. Curly-top of stock. 



Improved Wisconsin All Seasons, and Penn State Ballhead. Stock varieties also 
vary in resistance. Control insects, especially aphids and cabbage worms, which 
transmit the viruses. Use malathion and DDT at about 5-day intervals. Or grow 
seedlings under fine screening. See under Blackleg (above) . 

IS. Black Ringspot, Ring Necrosis — Symptoms variable. Small, yellow then black, 
concentric rings or spots on cabbage and older broccoli leaves. Leaves may curl, 
crinkle, and drop early. Small, light and dark green or yellowish, mottled areas on 
cauliflower, broccoli, stock, and honesty leaves. Turnip and horseradish leaves 
are yellowish, mottled, crinkled, and stunted. Irregular, dark green areas appear 
in the yellowed leaves. Roots may show black flecks when cut. Colored stock and 
honesty flowers show light flecks and streaks. Control: Same as for Mosaics (above) . 
If practical, surround the seedbed with screening to keep out insects. 

19. Curly-top, Brittleroot (primarily horseradish and stock) —Western half of the 
United States. Outer and later the inner leaves are narrow, curled, and puckered; 
roll inward and wilt. Stock plants are stunted and bushy. May turn yellow, white 
or purple, wilt and die in 2 or 3 weeks. When cut, horseradish roots are yellowish- 
tan with a ring of black dots in the center tissue. Roots later become brown to 
black and brittle. See Figure 87. Control: Destroy infected plants when first found. 
Plant virus-free horseradish roots. Plant early. Control leafhoppers which transmit 
the virus by spraying weekly with DDT and malathion. See under Blackleg 
(above) . 



160 CABBAGE 

20. Aster Yellows — See (18) Yellows under General Diseases. 

21. Scab (primarily cabbage, radish, rape, rutabaga, and turnip) —Rough, raised, 
scabby areas on the surface of the root. Control: Work plenty of organic matter 
into the soil. See under Beet and Potato. 

22. Root Rots, Black Root — General on radish. Leaves may discolor, wilt, and die. 
Plants may wilt easily or suddenly collapse. Roots and crown often decay. Dark 
spots at base of side roots. Spots enlarge to form metallic gray to black areas on 
the fleshy root. Entire root system may die. Fleshy root may be distorted, con- 
stricted, and turn black. Most common on the White Icicle-type radish. Control: 
Avoid heavy, wet, poorly drained soil. Treat the soil with a soil fumigant (e.g., 
Vapam, V.P.M. Soil Fumigant, Mylone, or formaldehyde) before planting (see 
pages 404-44) . Grow resistant radish types (e.g., colored and late varieties) . Rotate 
3 or 4 years with plants outside the cabbage family. Burn or plow under deeply 
all crop debris after harvest. Treat seed as for Blackleg (above) . 

23. Whiptail, Molybdenum Deficiency (primarily cauliflower, broccoli, cabbage, and 
Brussels sprouts in very acid, heavily fertilized soils) — Leaves long and narrow, 
ruffled, thickened, grayish-green, and very brittle. Plants stunted. If severe, head 
may be absent. Control: Have the soil tested. Apply hydrated lime so soil reac- 
tion (pH) will be near neutral. The addition of about 1 ounce of ammonium 
molybdate per 1,000 square feet has given good control. May apply with fertilizer, 
in transplant water (1 ounce to about 12 gallons of water) , or through foliar 
sprays. Check with a local grower, your county agent, or extension horticulturist. 
Varieties differ considerably in resistance. 

24. Powdery Mildew — White, powdery mold patches on leaves and stems. If severe, 
leaves may be distorted, yellow to brown, and drop early. Control: If serious 
enough, apply sulfur or Karathane. Otherwise same as for Blackleg (above) . 

25. Crown Gall — See under Asparagus, and (30) Crown Gall under General Diseases. 

26. Rust (garden cress, mustards, peppergrass, smelowskia, stanleya) — Small, yellow- 
ish spots on the leaves. Alternate host: wild grasses. Control: None usually nec- 
essary. 

27. V erticillium Wilt — Plants may or may not be stunted. Lower leaves turn yellow 
and wilt. Disease progresses up the stem. Dark streaks occur inside the stem. See 
(15B) Verticillium Wilt under General Diseases. Control: Plant in clean or steri- 
lized soil (pages 437-44) . 

28. Web Blight — Southeastern states. See under Bean. 

29. Oedema, Intumescence — Primarily an indoor problem with broccoli, Brussels 
sprouts, cabbage, cauliflower, and kale. Small wartlike or ridgelike growths on 
the underside of leaves. Corresponding upper side may be depressed. The growths 
become white, later turn yellow or brown and become corky in texture. Permanent 
injury is rare if environmental conditions are changed. Control: Maintain an even 
soil moisture supply. Increase air circulation. Avoid overwatering and forcing 
plants too rapidly. Avoid use of copper sprays. Plant where winds will whip plants. 

30. Other Root-feeding Nematodes (dagger, lance, naccobus, pin, reniform, root-lesion 
rot, spear, spiral, sting, stubby-root, stylet or stunt) — Mostly in southern states. 
Associated with sickly, stunted plants. Roots short, bushy, and die back. Control: 
Same as for Root-knot (above) . 



CALIFORNIA-HYACINTH 161 

CACTUS: CEREUS (many diverse species); SAGUARO (Cereus, Carnegiea); 

BARREL, STAR, SEA-URCHIN (Echinocactus or Ferocactus); THANKSGIVING, 

CRAB (Epiphyllum); PINCUSHION, FISHHOOK (Mammillaria); PRICKLYPEAR, 

CHOLLA, TUNA (Opuntia); ORGAN-PIPE (Pachycereus or Lema/reocereus;,- 

CHRISTMAS (Schlumbergera); ZYGOCACTUS 

1. Corky Scab — Pale, yellowish-green spots on the stems and shoots which often be- 
come irregular corky or rusty areas and may become sunken. Spots may remain 
smooth and grayish-white. Shoots may die. Control: Avoid overwatering, over- 
crowding, and applying too much fertilizer at one time. Avoid low potassium and 
high sodium content in the soil; keep the calcium level high. Plant in well-drained, 
sandy soil. Increase the light and air circulation. Decrease air humidity. 

2. Glassiness — Dark green, somewhat transparent spots which finally turn black. 
Shoots may die back. Otherwise same as for Corky Scab (above) . 

3. Stem and Root Rots, Cutting Rots, Wilts, Anthracnose, Cladode Rot, Seedling 
Blight — Cuttings, stems, and branches discolored (yellow, light to dark green, 
brown, or black) or spotted, gradually or suddenly wilt and rot. May become 
slimy and collapse (Bacterial Soft Rot) . A gray or black mold may grow on af- 
fected tissues. Roots decay. May be associated with nematodes (e.g., cyst, lance, 
root-knot, root-lesion, spiral, stylet or stunt) . Control: Cut out and destroy infected 
plant parts. Plant in sterilized soil (pages 437-44) . Avoid overwatering and wound- 
ing plants. Keep down air humidity. Sterilize seeds and disease-free cuttings by 
dipping in normal Semesan solution for 5 minutes before planting. Captan sprays 
at 10- to 14-day intervals may be beneficial. Keep water off aboveground parts. 

4. Bud Drop — Buds fall early, especially on Christmas cacti. Plants may be stunted. 
Control: Fertilize adequately. Maintain uniform soil moisture. Avoid large tempera- 
ture changes, cold drafts, and cold water on the foliage. 

5. Scorch, "Sunscald" — Segments turn reddish-brown and die. Young spots are "zoned" 
with grayish-brown, cracked centers. Control: Avoid high temperatures and too 
much sun. Otherwise same as for Bud Drop (above) . 

6. Black Mildew — Florida. See (12) Sooty Mold under General Diseases. 

7. Root-knot, Cyst Nematode — See (37) Root-knot under General Diseases. 

CAESALPINIA - See Honeylocust 

CALABASH -See Cucumber 

CALADIUM-See Calla 

CALATHEA-See Rabbit Tracks 

CALCEOLARIA — See Snapdragon 

CALENDULA — See Chrysanthemum 

CALIFORNIA-BLUEBELL - See Phacelia 

CALIFORNIA FREMONTIA - See Phoenix-tree 

CALIFORNIA FUCHSIA - See Evening-primrose 

CALIFORNIA-HYACINTH -See Brodiaea 



162 CALIFORNIA-LAUREL 

CALIFORNIA-LAUREL -See Avocado 

CALIFORNIA-POPPY -See Poppy 

CALIFORNIA-ROSE - See Morning-glory 

CALIFORNIA SWEETSHRUB -See Calycanthus 

CALLA [COMMON, GOLDEN, PINK, WHITE], CALLA LILY (Zantedeschia); 

CHINESE EVERGREEN (Aglaonema); ANTHURIUM; DRAGONROOT, 

JACK-IN-THE-PULPIT (Arisaema); CALADIUM; DASHEEN, ELEPHANTS-EAR 

(Colocasia); DIEFFENBACHIA; HOMALOMENA; CERIMAN (MonsferaJ; 

NEPHTHYTIS or SYNGONIUM; PHILODENDRON (many species and 

horticultural varieties); POTHOS or IVY-ARUM (Sc'mdapsus); YAUTIA, 

MALANGA (Xanthosoma) 

1. Bacterial Soft Rot, Leafstalk Rot (caladium, calla, dasheen, dieffenbachia) — Slimy r 
wet, often foul-smelling rot of the stem, leaf stalks, flower stalks, and underground 
parts. Leaves and flower stalks may suddenly wilt, turn yellow or brown, collapse, 
and die. Control: Destroy infected plants and rotted corms, rhizomes or tubers. 
Rotate. Plant dormant, disease-free calla corms or rhizomes soaked 30 to 60 
minutes in a 1:1,000 solution of mercuric chloride or formalin (1 to 50 dilution 
with water) . Soak dieffenbachia canes in streptomycin (200 parts per million) 
for 15 minutes. Wash with running water and plant shallow in light, well-drained 
soil, sterilized if possible (pages 437-44) , or where disease has not been present in 
the past. Keep the starting temperature above 70° F. and below 90° F. Avoid in- 
juries to plants, overwatering, and excessive nitrogen fertilization. Spraying every 
4 to 5 days with streptomycin, starting when the first symptoms appear, may be 
beneficial. Keep down the humidity. Propagate only from disease-free plants. 

2. Tuber, Corm, Stem (Cane) , Root and Rhizome Rots, Cutting Rots — Plants often 
stunted; leaves turn yellowish, later wither and die. Plants may not blossom or 
flowers may be deformed and decayed. Underground plant parts, or stem at the 
soil line, may rot. Plants collapse or are easily pulled up. See Figure 88. Control: 
Same as for Bacterial Soft Rot (above) . Commercial growers dip 2-foot sections of 
hardened dieffenbachia canes (1 to I1/2 inches in diameter) in hot water (120° F.) 
for 40 to 60 minutes. Canes are cooled and placed in sterilized sphagnum moss un- 
til new growth starts. The canes are then cut into pieces, each with a single bud, 
and planted. Soak dormant caladium tubers in hot water (122° F.) for 30 
minutes. Cool and plant in clean soil. Treat philodendron canes as for Bacterial 
Leaf and Stem Rot (below) . Dip hardened bare-root nephthytis (Syngonium) in 
hot water (120°F.) for 30 minutes. Cool and plant in sterilized soil. Take tip cut- 
tings from Chinese evergreen. Drench soil with mixture of Terraclor 75 per cent (1 
tablespoon per gallon of water) and ferbam 76 per cent (I1/9 tablespoons per 
gallon) . Use 1 pint per square foot. 

3. Root-knot, Other Nematodes (burrowing, root-lesion or meadow, spiral) — Internal 
discolored spots may be evident in caladium tubers. Plants may be sickly and 
stunted, gradually decline in vigor due to stubby, discolored roots. Control: 
Nurserymen soak bare-root philodendron and Chinese evergreen plants in hot 
water (122° F.) for 10 minutes before planting. Soak dormant caladium tubers as 
for Tuber Rot (above) . 

4. Spotted Wilt (calla) — Numerous, whitish-yellow flecks, spots, streaks, and even 
zoned rings on the leaves, flower stalks, and flower buds. Leaf spots may later 
turn brown. Leaves and flowers may be twisted and deformed. Pale greenish 



CALLA 



163 



blotches and streaks form on white flowers and on green buds. Control: Destroy 
infected plants when first found. Plant disease-free nursery stock. Control thrips 
with frequent DDT or malathion sprays. Keep down weeds. 

5. Mosaics — Leaves may be curled, show a yellowish mottle. Plants are stunted. 
Control: Same as for Spotted Wilt (above) . Control the virus-carrying aphids with 
malathion sprays. 

6. Leaf Spots, Anthracnose, Leaf and Flower Blight — Small to large, round to irregu- 
lar, spots of various colors on the leaves, flower stalks, and flowers. Spots may en- 
large and run together forming irregular blotches. Severely infected leaves may 
wilt, wither, and die prematurely. Certain spots have a border of a different color. 



Fig. 88. Root rot of calla. 




Control: Pick off and destroy severely spotted leaves. Keep down weeds. Indoors, 
avoid sprinkling the foliage, overcrowding, and overwatering. Keep the tempera- 
ture and humidity as low as practical. Control insects with a mixture of DDT 
and malathion. Apply ferbam, zineb, maneb, or captan sprays during rainy periods. 

1 . Bacterial Leaf Spot or Rot of Dieffenbachia — Small, yellow to yellowish-orange 
spots on the leaves. Centers of spots may be dull and watery-green. In wet weather 
the spots often enlarge and run together. Leaves may turn yellow, wilt, and die. 
During dry weather the spots remain small, dry, reddish-brown specks. Control: 
Pick off and burn severely spotted leaves. Space plants. Keep water off the foliage. 
Lower the air temperature. Spraying with streptomycin may be beneficial. 

8. Bacterial Leaf and Stem Rot of Philodendron — Small, irregular, water-soaked 
spots on leaves and stem. Spots enlarge rapidly during warm, moist weather. 
Leaves and leaf stalks may rot, collapse, and become mushy. Control: Remove and 
burn infected plant parts when first found. Destroy dilapidated plants. Scrub and 
thoroughly dry containers before reusing. Plant in sterilized soil (pages 437-44) . 
Where practical, spray at 5- to 10-day intervals, using streptomycin (200 parts per 
million) following the manufacturer's directions. Commercial growers control 
Stem Rot by soaking propagating canes for 30 minutes in hot water (120° F.) . 
Canes are then cooled and rooted in sterile sphagnum moss. 



164 CALLIANDRA 

9. Philodendron Leaf Yellowing, Dieback — Indoor problem. Leaves may be stunted, 
turn yellow, and drop early. Shoot tips may die back. Control: Increase light and 
humidity. Avoid overfertilizing, overwatering, and planting in heavy, poorly 
drained soil. Repot plants if needed. 

10. Rust (Jack-in-the-pulpit) —Small, lemon-yellow pustules on the leaves and spathe. 
Foliage later turns yellow and dies. Plants do not flower. Control: Pull up and burn 
infected plants. The rust fungus is perennial. 

1 1. Sooty Mold — See (12) Sooty Mold under General Diseases. 

CALLIANDRA, FALSE-MESQUITE, POWDER-PUFF TREE (Calliandra ) 

1. Root Rot — See (34) Root Rot under General Diseases. 

2. Rust (false mesquite) — Arizona. See (8) Rust under General Diseases. 

CALLICARPA — See Lantana 

CALLIRHOE - See Hollyhock 

CALLISTEPHUS-See Chrysanthemum 

CALLUNA-See Heath 

CALOCHORTUS - See Mariposa Lily 

CALONYCTION - See Morning-glory 

CALYCANTHUS, CAROLINA ALLSPICE, MOUNTAIN SPICEWOOD, 
CALIFORNIA SWEETSHRUB (Ca/ycanfhusJ 

1. Twig and Branch Canker — See under Maple, Chestnut, and (22) Stem Blight 
under General Diseases. Prune out and burn infected parts. 

2. Crown Gall — See under Apple, and (30) Crown Gall under General Diseases. 

3. Powdery Mildew — See (7) Powdery Mildew under General Diseases. 

CAMASS (Camassia) — See Colchicum 
CAMELLIA [COMMON, SASANQUA ] (Camellia) 

1. Flower B light — Widespread in southern states and along the Pacific Coast. Nu- 
merous, small, brown specks or spots on flowers. Whole flower soon turns dull 
brown, withers, and drops. Large, black bodies (sclerotia) form in the center of 
old flowers and serve to perpetuate the causal fungus. See Figure 89. Control: 
During early winter apply Terraclor (PCNB) dust or spray to the soil surface or 
leaf litter beneath plants and an area 10 feet beyond. Follow the manufacturer's 
recommendations. Repeat one month later. Remove and burn all fading flowers 
as soon as disease is evident. During bloom apply zineb or Thylate (1 tablespoon 
per gallon) at 3-day intervals if the period is rainy. Buy only certified, disease- 
free, bare-rooted plants. Before planting remove and burn all flower buds showing 
color. 

2. Dieback, Cankers, Graft Blight — Widespread and serious in southern states. Foli- 
age wilts, turns dull green, and dies from slightly sunken, sometimes blackened 
and dead cankers on the twigs and branches. Affected parts turn brown and die 
back. Control: Cut out and burn diseased stems several inches below the canker. 
Make flush cuts just below vigorous side branches. Cut out cankers on larger 
branches. Dip scion and grafting tools in a ferbam or captan solution (3 table- 
spoons per gallon of water) . Avoid wounding stems, overcrowding, overwatering, 
and too high a humidity. Captan, zineb, thiram, or fixed copper sprays applied just 



CAMELLIA 



165 



before wet periods should prevent infections. Grow resistant varieties, e.g., Governor 
Moulton and Professor Sargent. Check with your nurseryman, extension horticul- 
turist, or plant pathologist. 
3. Leaf Spots, Leaf Blight, Spot Anthracnose or Scab — Widespread outdoors in rainy 
seasons. Small to large, round to irregular, yellow, brown, black, gray, purplish, or 
silvery spots on the leaves. Often with a distinct margin. Spots may enlarge and 
run together forming blotches. Infected leaves may drop early. Twigs may die 
back. See Figure 90. Control: Collect and burn infected leaves. Apply the same 




Fig. 89. Camellia flower blight 



Fig. 90. Camellia leaf spots. A. Angular 
spot, B. Concentric spot, C. White spot, D. 
Black spot. All 4 types of spots would 
never be found on the same leaf. 



fungicides as for Dieback (above) . Maintain a steady, even growth with a good 
root system. Avoid overcrowding, overwatering, and too high a humidity. Keep 
the soil acid (pH 4 to pH 5.5) . Avoid using too much lime. 

4. Sunscald — Primarily an outdoor problem. Silvery to faded green or brown areas 
with irregular margins form on the exposed leaves. Control: Provide light shade 
and protect against strong winds. 

5. Bud Drop — Widespread. Primarily an indoor problem. Buds turn dark and drop 
off. Due to unfavorable growing conditions (e.g., spring frost, severe winter freez- 
ing, high or fluctuating temperature, cold drafts, malnutrition, irregular water 
supply, and low air humidity) . Control: Avoid overwatering when buds are form- 
ing. Keep the soil moisture as uniform as possible. Keep plants well supplied with 
nutrients. Avoid great fluctuations in temperature and soil moisture supply, cold 



166 



CAMELLIA 



drafts, low light, and excessive nitrogen fertilizer. Maintain the air humdity over 
50 per cent (page 28) . Repot only when roots are somewhat pot-bound. 
Bud Rot, Bud Blight, Botrytis Flower Blight — General. Buds and flowers rot. 
Often covered with a dense gray mold in wet weather. Commonly follows frost 
injury. Control: Increase the air circulation and decrease humidity. Provide a 
slightly warmer temperature. Space plants. Captan or zineb sprays should be bene- 
ficial. 

Black Mold or Mildew, Sooty Mold — Black, moldy patches on the leaves and 
twigs. Control: Spray with malathion or lindane to control aphids and other in- 
sects. Do not use DDT on camellias — it is injurious to them. 

Leaf, Bud and Stem Galls, Leaf Curl — Southeastern states. Buds and leaves are 
enlarged, thickened, distorted, and discolored white to reddish. May be covered 
with a whitish "bloom" on the underside which cracks and peels. Stems of new 




Fig. 91. Camellia leaf and stem gal 
(Courtesy Dr. V. H. Young) 



shoots may be thickened. See Figure 91. Control: Pick off and burn affected parts. 
Spray as for Dieback (above) . 
9. Root-knot — See (37) Root-knot under General Diseases. 

10. Infectious Leaf and Flower Variegation, Yellow Mo ttle — Irregular yellow specks, 
blotches, or mottling on the leaves and white splotches on the flower petals. Plants 
off color. May die back. Plants gradually lose vigor. Control: Destroy plants sus- 
pected of harboring a virus or at least separate from healthy plants. Propagate 
only from nonvariegated plants. Applications of an iron chelate (l/o teaspoonful 
per plant in a 3 gallon container every 6 to 8 weeks for 6 months) reduces virus 
symptoms on both leaves and flowers. The greening effect may be expected to last 
from 6 to 18 months. Iron sulfate may be substituted on acid soils. If plants are 
severely virus-infected, apply only small amounts of nitrogen fertilizer. 



CANNA 



167 



1 1. Chlorosis — Areas between the veins on the leaves turn yellow. See Figure 79. 
Leaves are curled. May be caused by a soil deficiency. Control: Fertilize adequately 
and regularly, based on a soil test. See also "Leaf and Flower Variegation" above. 
Soil should be kept acid (pH 4 to pH 5.5) . 

12. Root Rots — See (34) Root Rot under General Diseases. May be associated with 
nematodes (e.g., burrowing, dagger, lance, needle, pin, reniform, ring, root-knot, 
root-lesion, sheath, sheathoid, spiral, stubby-root, stylet or stunt) . 

13. Crown Gall — See (30) Crown Gall under General Diseases. 

14. Oedema — Primarily an indoor problem. Brown, rough, corky swellings on the 
leaves. Control: Maintain a uniform soil moisture. Avoid overwatering during 
cloudy, humid weather. Avoid overfertilizing. 

CAMOMILE — See Chrysanthemum 

CAMPANULA - See Bellflower 

CAMPAN U LATA - See Tulip 

CAMPHOR-TREE - See Avocado 

CAMPION — See Carnation 

CAMPSIS — See Trumpetvine 

CAMPTOSORUS - See Ferns 

CANARYBIRDFLOWER - See Nasturtium 

CANAVALIA - See Bean 

CANDLEBERRY - See Waxmyrtle 

CANDLES OF THE LORD - See Yucca 

CANDYTUFT - See Cabbage 

CANNA [EDIBLE and GARDEN], INDIAN SHOT (Canna) 

I. Bacterial Bnd Rot — Widespread on young plants early in the season. Flower buds 
and stalks may blacken and rot. Irregular, yellowish to brown, water-soaked streaks 
or spots may appear on the older leaves. Irregular, thin, expanding streaks develop 



HEALTHY 



Fig. 92. Bacterial bud rot of canna. Flower 
stalks may blacken and collapse. 




168 CANTALOUP 

along the leaves. Areas are white at first, then grayish-brown and finally black. 
Leaves appear ragged, spotted, or striped. May be distorted. Gummy sap may 
exude from blackened areas on the stalks. Flowers are ruined. See Figure 92. 
Control: Discard badly diseased plants. Soak dormant, healthy-appearing root- 
stocks for 2 hours in a 1:1,000 solution of mercuric chloride (see page 85 for 
precautions) . Avoid overcrowding, overwatering, and sprinkling foliage. Increase 
air circulation. Destroy infected buds early. Streptomycin bud and young leaf 
sprays may be beneficial. 

2. Mosaic — Irregular, light and dark green areas, or pale yellow stripes running 
outward from the center of the leaf to the margin. Areas may later turn a rusty- 
brown color. Leaves somewhat wrinkled and curled. Stems and flower parts often 
show yellowish bands. Plants may be stunted and late in flowering. Control: De- 
stroy infected plants as they will not recover. Keep down weeds. Control aphids, 
which transmit the virus, using malathion. The President variety is apparently 
immune. 

3. Rust — Yellowish to black powdery pustules on the lower leaf surface. Control: 
Generally not necessary. If severe, apply zineb. 

4. Tuber or Rhizome Rot, Crown Rot, Southern Blight — See under Calla. May be 
associated with nematodes (e.g., burrowing) . 

5. Bacterial Wilt — See under Tomato, and (15C) Bacterial Wilt under General 
Diseases. 

6. Yellows — Plants dwarfed with young leaves developing an irregular, diffuse, dull 
yellowing which turns bronze-colored with age. Control: See under Chrysanthemum. 

7. Leaf Spot — Small spots on the leaves. Control: Same as for Rust (above) . 

CANTALOUP - See Cucumber 

CANTERBURY-BELLS -See Bellflower 

CAPE-COWSLIP - See Tulip 

CAPE-HONEYSUCKLE - See Trumpettree 

CAPE-JASMINE -See Gardenia 

CAPE-MARIGOLD — See Chrysanthemum 

CAPSICUM -See Tomato 

CARAGAN A — See Honeylocust 

CARAWAY -See Celery 

CARDINAL CLIMBER -See Morning-glory 

CARDINALFLOWER - See Lobelia 

CARDOON - See Lettuce 

CARISSA-See Oleander 

CAROLINA JESSAMINE -See Butterflybush 



CARNATION 169 

CARNATION [FLORIST'S, HARDY], GARDEN PINKS [COTTAGE, GRASS, 

MAIDEN, RAINBOW], SWEET-WILLIAM (Dianthus); CORNCOCKLE 

(Aqrostemma); SANDWORT (Arenaria); BABYSBREATH (Gypsophila); 

MALTESE CROSS, EVENING CAMPION, RED and ROSE CAMPION, 

MULLEIN-PINK, JERUSALEM-CROSS, ROSE-OF-HEAVEN (Lychnis); HARDY 

GRASS PINK (Plumaris); CUSHION-PINK, FIRE-PINK, STARRY and MOSS 

CAMPION, CATCHFLY [ALPINE, SWEET-WILLIAM] (Silene) 

1. Fusarium Wilts, Yellows (carnation, pinks, sweet-william) —General and serious. 
Plants become grayish-green, wilt, turn greenish-gray, then yellow and die gradually 
at high temperatures. Young shoots are often yellowed and stunted. Plants are 
often one-sided. Inside of lower stem may show dark brown to red streaks when 
split. Roots are generally healthy. Stems are softened. Root-feeding nematodes 
(e.g., root-knot) may increase the severity of the wilt. Control: Take tip cuttings 
only from known, disease-free plants. Plant in sterilized soil, using disease-free 
seed or cuttings. Cultured carnation cuttings are available. Dig up and burn in- 
fected plants as soon as found. Indoors, keep the temperature and soluble salts low. 
Avoid overwatering, deep planting, and injuring plants. Varieties differ in resist- 
ance. 

2. Bacterial Wilt (carnation) — In hot weather the tops of infected plants suddenly 
wilt, are grayish-green, then yellowish and finally straw-colored. Inside of cut 
stems and roots may show yellow to brown, sticky streaks and ooze. Elongated, 
discolored stripes on stems which split open. Roots are rotted and sticky. Affected 
plants are easily pulled up. Root-feeding nematodes increase the severity of wilt. 
Control: Same as for Fusarium Wilt (above) . Keep the potassium and calcium 
levels high and the phosphorus level low. Avoid splashing when watering. Plant 
resistant varieties. 

3. V erticillium Wilt (carnation) — Uncommon. Symptoms much like Fusarium Wilt. 
Infected tissues turn brown. Stems are more or less solid. Control: Same as for Fu- 
sarium Wilt (above) . Occurs at lower temperatures than does Fusarium Wilt. 

4. Alternaria Leaf Spot and Branch Rot (carnation, Maltese cross, pinks, sweet-wil- 
liam) — General. Tiny purple spots on leaves and stems which later enlarge to 
form ash-gray to grayish-brown, dead, shrunken areas. Spots later become dark 
brown or black with a purple margin. Base of leaves and branches may rot, kill- 
ing the parts beyond. Rotted stems are firm and dark brown in color. Most com- 
mon on the lower leaves and branches. Control: Rotate. Destroy infected plant 
parts when seen and crop debris after harvest. Avoid fertilizers high in nitrogen 
and overcrowding. Take cuttings from the upper half of disease-free plants. In- 
doors, keep water off the foliage, decrease humidity, and increase the air circula- 
tion. Apply zineb, maneb, captan, dichlone, ziram, or phaltan at weekly intervals 
during wet periods. Start cuttings in a sterilized rooting medium. 

5. Stem and Root Rots, Southern Blight, Cutting Rot, Damping-off — General. Plants 
turn pale green or yellow, wilt, then brown and die. Stems rot, often break off 
near the ground line without yellowing. Cuttings may develop a soft, brown, 
mushy rot at the base and collapse. Seedlings wilt and topple over. Roots are often 
discolored and rotted. May be associated with nematodes. Control: Same as for Fu- 
sarium Wilt (above) . Dip cuttings in household bleach, Pano-drench, ferbam, or 
zineb solution before sticking. Treat sterilized soil by raking Terraclor dust into 
the top 2 inches of soil, or apply a soil drench of Terraclor 75 per cent wettable 
powder or Pano-drench. Follow the manufacturer's directions. Carnation varieties 
differ in resistance. Spray as for Alternaria Leaf Spot (above) . 

6. Rusts (babysbreath, carnation, evening campion, Maltese cross, pinks, red cam- 
pion, sweet-william) — General, especially where moist. Orange, reddish-brown, 




170 CARNATION 

or chocolate-colored powdery pustules on leaves, stems, and buds. Plants often 
stunted with curled-up leaves. Varieties differ in resistance. See Figure 93. Control: 
Same as for Alternaria Leaf Spot (above) , except use only zineb, maneb, ferbam 
and sulfur, or dichlone. Plant resistant carnation varieties. Dip cuttings in ferbam 



Fig. 93. Carnation rust. 



solution (2 tablespoons per gallon of water plus a spreader-sticker) before plant- 
ing. 

7. Mosaics, Mottle, Streak (carnation, pinks, sweet-william) — Widespread. Symptoms 
variable. Leaves show light and dark green to yellowish-white, red, or grayish- 
brown spots, streaks, mottling, and necking. Leaves may be curled and distorted. 
Light streaks or blotches may develop in colored flower petals of some varieties. 
Plant vigor, size, and flowering are often reduced. See Figure 32A under General 
Diseases. Control: Plant virus-free plants or cuttings. Destroy infected plants when 
first seen. By using malathion or lindane control aphids which transmit the viruses. 
Wash hands and cutting knife with soap and hot water before handling healthy 
plants. 

8. Ringspot — Uncommon. Symptoms variable. Carnation and lychnis leaves show 
rings, often zoned, or a pronounced mosaic mottling with some dead flecks. Carna- 
tion leaf margins are wavy. Older leaves may redden and curl. In sweet-william, 
the zoned rings on the leaves turn into a general mosaic with scattered, white 
spots. Control: Same as for Mosaics (above) . 

9. Curly-top (carnation, pinks, sweet-william) — See under Beet, and Figure 35A 
under General Diseases. Control: Same as for Mosaics (above) . Use mixture of 
DDT and malathion to control leafhoppers which transmit the virus. 

10. Aster Yellows (babysbreath, carnation, mullein-pink, sweet-william) —See under 
Chrysanthemum, and (18) Yellows under General Diseases. 

11. Other Leaf Spots, Anthracnose, Greasy Blotch — Small to large, pale, purplish, 
gray, brown, greasy, or grayish-green spots and blotches on leaves. Sometimes on 
stems and flowers. More common on the lower leaves which may wither and die. 
Control: Same as for Alternaria Leaf Spot (above) . 

12. Gray-mold Blight, Botrytis Flower Blight — Cosmopolitan in damp weather. Flower 
petals show soft, water-soaked areas which turn brown. Buds may rot and fail to 
open. Tops of plants may die back. A gray mold may grow on diseased areas in 
damp weather. Varieties differ in susceptibility. Common storage rot of flower 
petals and stems. Control: Carefully pick off and burn blighted flowers, buds, and 
stem tips. Apply captan, zineb, or ferbam, one to three times just before bloom. 
Destroy tops in the fall or after harvest. Indoors, keep water off the foliage and 
the humidity as low as practical. Increase air circulation and temperature. Avoid 
overcrowding plants. Apply a light misty spray of zineb (1 tablespoon per gal- 
lon) as the flowers are opening. 

13. Fusarium Bud Rot — Primarily a disease of carnation. Young buds fail to open. 
The interior of such buds is brown or pink, moist, and decayed. A white, cottony 
mold and mites may also be present. White varieties are more susceptible than 
colored ones. Control: Pick off and destroy infected buds when first found. Spray 
with malathion to control mites which spread the causal fungus from plant to 
plant. 



CARROT 171 

14. Anther or Flower Smut (arenaria, carnation, dianthus, Maltese cross, silene, sweet- 
william) — Anthers in flowers are filled with a blackish powder. Pistillate (female) 
flowers are aborted. Flower stalks are stunted and produce flower buds that are 
thick, squat, often split. Infected plants grow slowly, producing numerous second- 
ary shoots. Appear bushy. Control: Destroy infected plants before buds open. Take 
cuttings only from healthy plants. Most modern carnation varieties are resistant. 

15. Witches' -broom, Fasciation, Leafy Gall (babysbreath, carnation) —Fairly common 
but causes no serious damage. Leaves distorted and growth is stunted. See under 
Pea, and (28) Leafy Gall under General Diseases. 

16. Powdery Mildew (arenaria, carnation) —Mealy, whitish mold growth on leaves, 
stems, and flowers. Varieties differ in resistance. Control: See under African-violet, 
and (7) Powdery Mildew under General Diseases. 

17. Crown Gall, Root and Stem Gall — Soft, gall-like overgrowths at graft or soil line. 
Plants may be girdled, wilt, and die. Control: Dig up and burn affected plants. 
Do not propagate from infected plants. Dip newly grafted plants and grafting 
knives in household bleach solution (2 to 6 ounces per gallon) for 2 minutes be- 
tween cuts. Carnation varieties differ in resistance. 

18. Root-knot, Cyst Nematode — Set (37) Root-knot under General Diseases. 

19. Leaf and Stem Nematode (carnation, sweet-william) — Leaves crinkled and stems 
swollen. See (20) Leaf Nematode under General Diseases. 

20. Other Root-feeding Nematodes (criconemoides, lance, pin, ring, root-lesion, spear, 
stylet) — Plants stunted. Blooming and root growth are reduced. Control: Plant in 
sterilized soil (pages 437-44) . 

21. Boron Deficiency — Tips of shoots are twisted, curled up, and may be deformed 
into witches'-brooms. Shoots get stuck trying to elongate. Control: Apply borax to 
soil using 1 ounce to 100 square feet. Water the borax in. Reapply as necessary. 
Check with your local florist or extension horticulturist. 

22. Downy Mildew (carnation) — California. Leaves pale and curl downward. A whit- 
ish mold forms on the underleaf surface in humid weather. Plants stunted. Control: 
Same as for Alternaria Leaf Spot (above) . 

23. Web Blight — Southeastern states. See under Bean. 

24. Bacterial Leaf Spot (carnation) — Widespread. Small, elongated, light gray leaf 
spots with water-soaked margins. Spots later become brown and sunken. Control: 
Same as for Bacterial Wilt (above) . Spray with phenyl mercury plus a spreader- 
sticker. 

CARNEGIEA-See Cactus 

CAROLINA ALLSPICE -See Calycanthus 

CAROLINA MOONSEED - See Moonseed 

CARPETGRASS — See Lawngrass 

CARPINUS-See Birch 

CARANDA — See Oleander 

CARROT (Daucus); PARSNIP (Pastinaca) 

l.Leaf Blights and Spots — General. Outer leaves and petioles turn yellow, then 
brown and wither due to a tan, gray, yellowish-green, reddish-brown, or black spot- 
ting. Spots may also occur on the petioles, stems, and flower parts. Whole top may 
die when spots enlarge and run together. Yield is reduced. Bacterial blight may 



172 CARROT 

cause dark, scabby cankers on carrot roots. Control: Plant in well-drained soil. Keep 
down weeds. Three- or 4-year rotation. Burn or bury tops after harvest. Plant 
disease-free seed or soak carrot seed in hot water (122° F.) for 15 to 20 minutes. Dry 
seed, then dust with captan, thiram, dichlone, or chloranil. Apply maneb, zineb, 
ziram, or fixed copper at 7- to 10-day intervals during rainy periods. 

2. Aster Yellows — Widespread. Younger and inner leaves are yellow, stunted, and 
twisted. Plants stunted, appear bunchy. Outer leaves have a bronzed, reddish, or 
purple color. Carrot is stunted, woody, and covered with many "hairy" roots. See 
Figure 34B under General Diseases. Control: Destroy first infected plants. Keep 
down weeds in and around the garden area. Spray or dust at 5-day intervals with 
DDT or methoxychlor and malathion to control leafhoppers which transmit the 
virus. Start when seedlings are 2 inches tall. Carrot varieties differ in resistance. 

3. Storage Rots, Root Canker — Cosmopolitan. Rots of various types, some watery, 
slimy, foul-smelling, and wet (Bacterial Soft Rot) . May be covered with a white, 
gray, tan, pink, blue, green, or black mold growth. Spread rapidly in damp, warm 
bins where roots are piled closely together. Rot may start at the crown or from 
a wound on the side of the root. See (29) Bacterial Soft Rot under General Diseases. 
Control: Three-year rotation. In the field, keep the nitrogen level on the low side 
and the potassium level high. Store roots as close to 32° F. as possible without ex- 
cessive humidity (90 to 95 per cent) . Dust roots lightly with thiram or captan and 
then store. Avoid free moisture in storage. Store only sound, blemish-free roots in 
layers with straw, dry leaves, or other dry filler material in between. Avoid in- 
juries. Spray or dust in the field as for Leaf Blights (above) . The storage area 
should be swept clean and then sprayed with copper sulfate solution (1 pound in 
10 gallons of water) before storing vegetables and fruit. Do not store carrots and 
apples together. For information on what to store and where it should be kept, 
check with your extension horticulturist. 

4. Seed Rot, Damping-off — General. Poor stand. Seeds rot. Seedlings wilt and col- 
lapse. Control: See under Leaf Blights (above) . In addition, apply aldrin or chlor- 
dane to the soil surface before planting and immediately work into the top 3 to 
6 inches. Avoid overwatering. Cultivate soil surface lightly. 

5. Root Rots — Plants may be stunted and sickly. Roots discolored and decayed. May 
follow attacks by the carrot weevil, carrot rust fly, growth cracks, nematodes (e.g., 
dagger, lance, naccobus, reniform, rot, root-lesion, stem, stubby-root, stylet) , in- 
juries, or other diseases. Control: Avoid overfertilizing. Plant late. Long rotation. 
Control other diseases. Treat soil with chlordane or aldrin following the manu- 
facturer's directions. See under Seed Rot (above) . Harvest early. Tolerant carrot 
varieties to Violet Root Rot are Chantenay and Chantenay Red Cored. Use disease- 
free seed. 

6. Root-knot, Cyst Nematode — General in southern states. Occasional in the rest of 
the United States. Localized areas of stunted plants. Small, gall-like swellings on 
roots. Taproot may be "forked," twisted, misshapen, and undersized. Yield is re- 
duced. See Figure 50A under General Diseases. Control: Rotate. If serious enough, 
fumigate in early fall using D-D, EDB, Nemagon, Vapam, Dorlone, or Telone, fol- 
lowing the manufacturer's directions. 

7. Watery Soft Rot, Cottony Rot, Sclerotinia Rot, Southern Blight — Widespread. 
See under Bean. Occurs in patches in the field. 

8. Scab — Dark brown areas on the root, often near the crown. Control: See under 
Beet and Potato. 

9. Parsnip Canker, Leaf Spot — May be serious in rainy seasons. Brown to reddish, 
roughened surface on shoulder or crown of the root, which later turns purplish- 
brown to black. Whole root may decay. Small, irregular, greenish-yellow leaf spots 



CASTORBEAN 173 

often with brown centers, may develop. Entire leaves may die and fall early. Con- 
trol: Plant in well-drained soil. Keep down weeds, especially wild carrot. Apply 
fixed copper, bordeaux (4-2-50), maneb, or zineb at 10-day intervals, starting 
when leaf spots are first seen. 

10. Mosaics, Motley Dwarf, Ringspot — Leaves mottled light to dark green and yel- 
lowed. Some rings or dead spots may appear in the leaves. Plants may be stunted 
with twisted petioles. Control: Same as for Aster Yellows (above) . Control aphids 
which transmit the viruses. Use malathion. 

1 1 . Curly-top — Western states. See under Beet, and (19) Curly-top under General 
Diseases. 

12. Root Cracking, Boron Deficiency — Young leaves are yellowed and malformed. 
Plants wilt readily. Longitudinal cracks often occur in carrot (root) when heavy 
rains follow a drought period, or when boron is deficient in the soil. Root may 
be stunted and woody. Control: Maintain as uniform a soil moisture as possible by 
watering during dry periods. Have the soil tested. If deficient in boron, apply 
borax as recommended by your county agent or extension horticulturist. 

13. Bacterial or Southern Wilt — Southern states. See under Tomato, and (15C) Bac- 
terial Wilt under General Diseases. 

14. Crown Gall — See (30) Crown Gall under General Diseases. 

15. Dozuny Mildew — Yellow spots develop on the upper leaf surface which darken 
with age. A yellowish mildew is found on the corresponding underside in damp 
weather. Control: Same as for Leaf Blights (above) . 

16. R ust — Small yellowish pustules on the leaves. Alternate host is bulrush (Scirpus). 
Control: Same as for Leaf Blights (above) . 

17. Web Blight — Southeastern states. See under Bean. 

18. Powdery Mildew (parsnip) —See (7) Powdery Mildew under General Diseases. 

CARTHAMUS - See Chrysanthemum 

CARUM-See Celery 

CARYA-See Walnut 

CARYOPTERIS - See Lantana 

CARYOTA-See Palms 

CASSABA, CASSABANA - See Cucumber 

CASSANDRA - See Blueberry 

CASSIA — See Honeylocust 

CASSIOPE - See Blueberry 

CASTANOPSIS - See Chestnut 

CASTILLEJA — See Snapdragon 

CAST-IRON PLANT -See Aspidistra 

CASTORBEAN (R/c/nus); CHINESE TALLOWTREE (Sapium); 
QUEENS-DELIGHT (Stillingia) 

I. Gray-mold Blight, Botrytis Blight — Eastern and southern states on castorbean. 
Occurs during humid, wet seasons. Small to large, pale brown to blackish spots on 



174 CATALPA 

leaves, stems, flower stalks, fruit clusters, and capsules over which a pale to olive- 
gray mold later grows. Blight usually occurs at blooming time. Control: Plant seed 
from disease-free castorbean plants. Where practical, carefully pick off and destroy 
fading flowers and infected parts. Burn tops in the fall. Castorbean varieties differ 
in resistance. Apply captan, zineb, thiram, or fixed copper one to three times, 5 to 
7 days apart. 

2. Fungus Leaf Spots, Capsule Mold — Round to irregular, white, gray, or brown 
spots and blotches on the leaves and capsules. Leaves and seed may wither and 
fall early. Control: Same as for Gray-mold Blight (above) . Tolerant castorbean 
varieties to Alternaria Leaf Spot: Baker 296, Dawn, and MW-1. 

3. Bacterial Leaf Spot of Castorbean — Southern states during rainy seasons. Brown 
to black, angular spots on the leaves. Control: Plant disease-free seed. Somewhat 
resistant varieties: Anjou, Baker 195, Illinois 48-36, and Western Oil Hybrid 9. 

4. Root Rots — See under Bean, Apple, and (34) Root Rot under General Diseases. 
Often associated with root-feeding nematodes (e.g., burrowing, root-lesion) . 

5. Root-knot — See (37) Root-knot under General Diseases. 

6. Bacterial Wilt or Brown Rot (castorbean) — Southeastern states. Plants wilt but 
may recover temporarily. Leaves shrivel, turn black, and drop early. Stalks and 
branches are blackened. Control: Grow plants in clean soil. Use disease-free seed. 

7. Seed Rot, Seedling Blight — Seeds rot. Seedlings become stunted, wilt, and collapse. 
Leaves are blighted. Control: Collect and burn infected plants. Rotate. Plant in 
warm, well-drained, sterilized soil (pages 437-44) . Spray during cool wet periods as 
for Gray-mold Blight (above) . Treat seed with thiram, captan, or chloranil. 

8. Stem and Crown Rots, Southern Blight (castorbean) — Stems discolored and rotted 
at or below the soil line. Plants die early. Control: Keep plants vigorous by ferti- 
lizing and watering. Plant in well-drained soil. Avoid overwatering and overcrowd- 
ing. Keep down weeds. 

9. Verticillium Wilt (castorbean) — Yellowish, then dead, areas form in the leaves 
between the veins. The disease progresses up the stem causing dying of the branches 
and blighting of the capsules. Control: Same as for Bacterial Wilt (above) . 

10. Crown Gall — See (30) Crown Gall under General Diseases. 

11. Seedling Red Gall — Texas. Small red galls develop on the leaves, petioles, and 
stems. Control: Pick off and burn affected parts. 

12. Rust (queens-delight) —Small yellowish spots or pustules on foliage. Alternate 
host is a grass (Panicum). Control: See (8) Rust under General Diseases. 

CATALPA [ COMMON or SOUTHERN, JAPANESE, MANCHURIAN, 

NORTHERN or WESTERN, UMBRELLA- ] (Catalpa); DESERT-WILLOW 

(Chilopus); JACARANDA; PODRANAEA 

l.Leaf Spots, Anthracnose, Spot A n thracnose — General in rainy seasons. Round to 
irregular, brown to black spots on the leaves. Spots may later fall out leaving 
holes. Leaves may wither and drop early. Control: Collect and burn fallen leaves. 
Apply three sprays, 2 weeks apart, starting as the leaves begin to unfold. Use fer- 
bam, thiram, captan, maneb, fixed copper, or bordeaux mixture (4-4-50) . 

2. Powdery Mildews (catalpa) — Powdery, white mold patches on leaves. If severe, 
leaves may wither and drop early. Control: If practical, spray twice, 10 to 14 days 
apart, using sulfur or Karathane. 

3. Wood Rots — Widespread. See under Birch, and (23) Wood Rot under General 
Diseases. 



CELERY 175 



4. Verticillium Wilt (catalpa) — Widespread. The leaves on one or more branches 
wilt, turn brown and hang downward or fall early. Purple to bluish-brown streaks 
are evident in the sapwood under the bark. Affected trees may die the first year 
or live for many years. Control: See under Maple. 

5. Root Rots — See under Apple, and (34) Root Rot under General Diseases. May 
be associated with root-feeding nematodes (e.g., burrowing) . 

6. Chlorosis (catalpa) — See under Maple. Occurs in alkaline soils. 

7. Leaf Scorch — Primarily in the Middle West. Follows hot, dry periods. See under 
Maple. 

8. Sooty Mold — See under Elm, and (12) Sooty Mold under General Diseases. 

9. Root-knot — See under Peach, and (37) Root-knot under General Diseases. 

10. Crown Gall — See (30) Crown Gall under General Diseases. 

11. Dieback, Canker — See under Apple and Maple. 

12. Seedling Blight, Damping-off — See under Pine. 

CATASETUM - See Orchids 

CATCHFLY - See Carnation 

CATCLAW - See Honeylocust 

CATHA — See Bittersweet 

CATNIP -See Salvia 

CATTLEYA-See Orchids 

CAULIFLOWER -See Cabbage 

CAULOPHYLLUM - See Barberry 

CEANOTHUS - See New Jersey-tea 

CEDAR, CEDRUS-See Pine 

CEDRELA — See Chinaberry 

CELANDINE - See Poppy 

CELASTRUS - See Bittersweet 

CELERY, CELERIAC (Apium); DILL (Anefhum); 

CHERVIL {Anthriscus or Chaerophyllum); CARAWAY (Carum); 

CORIANDER (Coriandrum); ERYNGO, SEA HOLLY (Eryngium); 

FENNEL, FINOCCHIO (Foeniculum); SWEET-JARVIL, ANISE-ROOT 

(Osmorhlza); PARSLEY (Petroselinum); ANISE (Pimpinella); 

BLUE LACEFLOWER (Trachymene or Didiscus) 

I. Leaf Blights and Spots — General, may be serious. Round to irregular, brown, yel- 
lowish-brown, ash-gray, yellow, tan, reddish-brown, or water-soaked spots on the 
leaves, petioles, leaf stalks and stems. If numerous, leaves may turn yellow to 
brownish-black, wilt, shrivel, and die. Infected seed may be discolored. Quality 
and yield may be reduced. See Figure 17C under General Diseases, Control: Plant 
in well-drained soil. Space plants. Keep down weeds. Do not work among wet 
plants. Celery varieties differ in resistance: Emerson Pascal has moderate resistance 
to Early and Late Blights while Giant Pascal and White Plume have moderate re- 
sistance to Late Blight. Burn or bury tops after harvest. If practical, plant rows 



176 CELERY 

north and south. Plant certified, disease-free celery seed, or soak celery seed (also 
celeriac) in hot water at exactly 118° F. for 30 minutes. Dry seed and dust with 
thiram, captan, chloranil, or Semesan. Dust other seed with thiram or Semesan. 
Three-year rotation, especially of the seedbed. Apply ferbam, thiram, maneb, 
zineb, ziram, dichlone, Dyrene, or fixed copper sprays at 5- to 7-day intervals in 
the field during wet weather. Use ziram, ferbam, or thiram in the seedbed. If Bac- 
terial Blight is a problem, add streptomycin (25 to 50 parts per million) to leaf 
blight sprays starting in the seedling stage. 

2. Seed Rot, Damping-off — Cosmopolitan. Seeds rot. Poor stand. Seedlings wilt and 
collapse. Control: Treat seed as for Leaf Blights (above) . Spray seedlings at 5- to 
7-day intervals using ziram, ferbam, thiram, or fixed copper. Plant in sterilized 
soil (fumigated with chloropicrin or methyl bromide) where feasible. 

3. Fusarium Wilt, Yellows (celery, dill, parsley) — General, except in southern 
states. Symptoms vary with the particular fungus strain. Plants yellowish and 
stunted. Growth is often one-sided. Seedlings wilt and die. Stalks brittle and have 
a bitter taste. Yellowish to reddish-brown or nearly black strands inside stems. 
Roots may decay. Control: Plant healthy seedlings in clean soil. Use resistant 
celery varieties in infested soil: Cornell No. 19, Easy Blanching, Emerson Pascal, 
Florida Golden, Forbes Golden Plume, Giant Pascal, Golden 99, Golden Pascal, 
Kilgore's Pride, Masterpiece, Michigan Improved Golden, Michigan State Green 
Gold, Pascal 284, Slow Bolting Green No. 12, Supreme Golden, Tall Golden 
Plume, Utah 15, and Woodruff's Beauty where adapted. Check with your extension 
horticulturist. 

4. Aster Yellows — Widespread. Inner, heart leaves dwarfed, yellowed, and twisted. 
Whole plant may be bushy, gradually turns yellow. Petioles are upright, brittle, 
and commonly crack. Control: See under Carrot, and (18) Yellows under Gen- 
eral Diseases. 

5. Root-knot — Widespread. Dill is very susceptible. See (37) Root-knot under Gen- 
eral Diseases. Control: Plant disease-free seed and transplants grown in clean or 
pasteurized soil (see "Soil Treatment Methods and Materials" in the Appendix) . 

6. Stem Rot, Pink Rot, Storage Rots — Cosmopolitan. Cut celery and parsley butts 
and stalks may become discolored and soft or slimy. Diseased areas may be covered 
with a cottony, pink, gray, bluish-green, or black mold. In the field, stems and 
leaf stalks suddenly wilt and collapse. A cottony mold may cover the rotted area 
at the ground line. See (29) Bacterial Soft Rot, and (21) Crown Rot under Gen- 
eral Diseases. Control: See under Carrot. Spray as for Leaf Blights (above) . Ap- 
ply Terraclor (PCNB) dust or spray in the field following the manufacturer's di- 
rections. 

7. Mosaics, Calico, Yellow Spot, Motley Dwarf, Streak — Symptoms variable. Plants 
often bunchy and stunted, with curled and twisted stalks. Leaves often mottled, 
spotted, or striped with yellow and green, crinkled, twisted, narrower than 
normal, cupped downward, and a sickly greenish-yellow or grayish color. Green 
and yellow zigzag bands and green "islands" may develop in yellow areas of the 
leaves (Calico) . Leaf stalks may turn brown and shrivel. Control: Plant virus-free 
seedlings. Destroy first infected plants. Keep down weeds. Control the aphids 
which transmit the viruses using malathion or nicotine sulfate. 

8. Blackheart, Heart Rot (celery, fennel, parsley) — General. Inner, heart leaves die 
at tips and turn dark. Later all the center leaves and petioles are affected. Outer 
stalks are never involved. Bacterial Soft Rot may follow. Common in low spots in 
the field. Control: Plant rows north and south in well-drained soil. Water during 
dry periods. Harvest promptly at maturity. Avoid overfertilization with nitrogen 



CENTAUREA 177 

(especially sodium nitrate) . If practical, apply sprays of calcium chloride (3^ to 
I1/2 ounces per gallon of water) or calcium nitrate (\i/ 2 to 3 ounces per gallon) , 
into the heart leaves at weekly intervals, starting 5 to 7 weeks before harvest. Re- 
sistant celery varieties: Cornell 19, Emerson, Florida Golden, Golden Pascal, 
Golden Phenomenal, Salt Lake, and Winter Queen. 
9. Stem-cracking, Brown Checking, Boron Deficiency — Occasional in all commercial 
celery districts where soil is heavy and alkaline. Younger and inner leaves brownish 
and mottled along the margins. Long, brown streaks may appear on the stems. 
Ragged, crosswise cracking of leaf stems. Stems (petioles) stiff, brittle, and some- 
times bitter. Roots turn brown. Celeriac crowns are often hollow. Control: Have 
soil tested and apply borax or boric acid as recommended. Resistant celery vari- 
eties: Columbia No. 4130, Dwarf Golden Self Blanching, Easy Blanching No. 5178, 
Giant Pascal, and Golden Self Blanching. Avoid excessive use of fertilizer high in 
nitrogen or potassium in boron-deficient soil. 

10. Spotted Wilt — Numerous small, yellow to orange spots on the older leaves. The 
spots later turn brown. Leaves may wither and die. Plants often dwarfed. Control: 
See under Tomato, and (17) Spotted Wilt under General Diseases. 

1 1. Curly-top — Attacks celery, celeriac, chervil, coriander, fennel, and parsley. See 
under Beet, and (19) Curly-top under General Diseases. 

12. Ringspot (celery) —Yellowish rings or spots, line or zig-zag patterns, on crinkled 
leaves. Control: Same as for Mosaics (above) . 

13. Root Rots, Basal or Crown Rot — Foliage often stunted and sickly. Roots, leaf stalk 
bases and crown may decay and turn red, brown, black, or bluish-green. Root- 
feeding nematodes may provide wounds by which rot-producing organisms enter. 
Control: Same as for Leaf Blights and Root-knot (both above) . 

14. Stem Nematode (celery, parsley) —See (20) Leaf and Stem Nematode under Gen- 
eral Diseases. 

Ib.Verticillium Wilt (celery, celeriac, parsley) -See (15B) Verticillium Wilt under 
General Diseases. 

16. Rust (anise, anise-root, sweet-jarvil) —General. See (8) Rust under General Dis- 
eases. 

17. Leaf Smut, White Smut (eryngium) -See (13) White Smut under General Dis- 
eases. 

18. Downy Mildew — Attacks celery, chervil, fennel, and parsley. See under Carrot. 
Control: Same as for Leaf Blights (above) . 

19. Bacterial Petiole Spot (celery) —Water-soaked, sunken spots develop on the in- 
ner and outer petioles. The spots later enlarge up to an inch or so in diameter 
and turn yellow to deep brown. Cornell 19 and Utah 52-70 are very susceptible. 
Control: Use copper sprays to control foliage diseases. Use throughout the sea- 
son. Otherwise same as for Leaf Blights (above) . 

20. Root-feeding Nematodes (awl, pin, root-lesion, sheath, sting, stubby-root, stylet or 
stunt) —Associated with sickly, stunted, unthrifty plants. Roots often short and 
stubby. Often found together with Root-knot. Control: Same as for Root-knot 
(above) . 

CELOSIA-See Cockscomb 

CELTIS-See Hackberry 

CELTUCE -See Lettuce 

CENTAUREA - See Chrysanthemum 



178 CENTIPEDEGRASS 

CENTiPEDEGRASS-See Lawngrass 

CENTRANTHUS-See Valerian 

CENTROSEMA - See Pea 

CENTURYPLANT (Agave)} FURCRAEA; WILD TUBEROSE, 
SPICELILY (Manfreda) 

1. Anthracnose, Black Rot — Round, sunken, dark spots with a raised border on the 
leaves. Spots may enlarge and run together causing the whole leaf to die. Control: 
Pick off and burn infected leaves. Indoors keep water off the foliage. If practical, 
apply copper, zineb, or maneb several times, 10 days apart, during rainy periods. 

2. Leaf Spots, Leaf Blights, or Scorch — Spots and blotches of various colors and 
shapes on leaves. Spots may enlarge and cover the entire leaf. Control: Same as 
for Anthracnose. Indoors raise the temperature and maintain a uniform soil 
moisture. 

3. Gray-mold Blight — See under Begonia. Follows overwatering or chilling. Control: 
Avoid overwatering or chilling. Space plants to increase air circulation. 

4. Root-knot — See (37) Root-knot under General Diseases. 

b.Rnst (manfreda) — Small yellowish pustules on leaves. Control: Same as for An- 
thracnose (above) . 

CEPHALANTHUS - See Buttonbush 

CEPHALOTAXUS - See Japanese Plum-yew 

CERCIS - See Honeylocust 

CEREUS-See Cactus 

CERIMAN-See Calla 

CHAENOMELES - See Apple 

CHAEROPHYLLUM - See Celery 

CHAMAECYPARIS - See Juniper 

CHAMAEDAPHNE - See Blueberry 

CHASTE-TREE - See Lantana 

CHAYOTE-See Cucumber 

CHECKERBERRY - See Heath 

CHECKERAAALLOW - See Hollyhock 

CHEIRANTHUS - See Cabbage 

CHELIDONIUM-See Poppy 

CHELONE — See Snapdragon 

CHERRY, CHERRY-LAUREL -See Peach 

CHERVIL -See Celery 



CHINABERRY 179 

CHESTNUT [AMERICAN, CHINESE, JAPANESE, SPANISH or EUROPEAN], 
CHINQUAPIN (Castanea); GOLDEN CHINQUAPIN (Castanopsis) 

1. Chestnut Blight or Canker— General. Reddish-orange, yellowish-brown or brown, 
slightly sunken, cracked, girdling cankers on twigs, branches, and trunk. Blight 
quickly spreads down into the trunk. Leaves of affected portions suddenly turn 
yellow and brown, wilt, die, and hang downward on the branches. Spread by in- 
sects and birds. This disease has practically eliminated the American and Spanish 
or European chestnuts from the United States. Control: Plant the resistant Chinese 
and Japanese chestnuts. Resistant varieties: Alaling, Alamoore, Blackbeauty, and 
Ching Chow. 

2. Leaf Spots, Anthracnose — Spots of various sizes and colors on the leaves. Not 
serious. Spots may drop out or enlarge and run together causing leaves to blight. 
Control: Collect and burn leaves in the fall. If practical spray as for Maple An- 
thracnose. 

3. Twig Blights, Cankers, Dieback — Widespread. Discolored, sunken to swollen 
cankers on twigs, branches, and trunk. May girdle and kill parts beyond. Leaves 
on girdled branches wilt, turn brown, and die. Growth is stunted. Trees may be 
deformed. Most serious on young trees. Control: Maintain vigor by fertilizing 
and watering. Plant in well-drained soil where air circulation is good. Prune out 
and burn dead or cankered wood, making cuts at least 6 inches below any sign of 
infection. Avoid leaving stubs. For large cankers on the trunk contact a competent 
tree surgeon. Paint over wounds promptly with a good tree wound dressing. 
All varieties and seedlings are resistant to the common twig cankers (Cryptodi- 
aporthe and Botryosphaeria) when grown on proper sites. Remove and burn se- 
verely diseased trees. Spray as for Leaf Spots (above) . 

4. Wood Rots — See (23) Wood Rot under General Diseases. 

5. Root Rots — Trees decline in vigor. Foliage is thin and sickly. Leaves turn yellow, 
wither, and drop early. See under Apple, and (34) Root Rot under General Dis- 
eases. Most varieties and seedlings are highly resistant to Phytophthora Root Rot. 

6. Powdery Mildews — Powdery, grayish-white mold growth on leaves and young 
shoots. If severe, leaves may turn yellow and wither. Control: If serious enough, 
spray twice, 10 days apart, using Kara thane or sulfur. 

7. Oak Wilt - See under Oak. 

8. Leaf Blister (chinquapin) — See under Oak. 

9. Blossom-end Rot of Nuts (Chinese chestnut) — Brown then black rot of blossom- 
end of fruit. Rot area often is later covered with a pale grayish mold. Control: 
Spray developing fruit with captan or zineb. Keep trees well pruned. Individual 
trees vary greatly in resistance. 

CHICORY -See Lettuce 

CHILOPUS-See Catalpa 

CHINA - ASTER — See Chrysanthemum 

CHINABERRY, CHINA TREE (Melia); CEDRELA, CHINESE CEDRELA (Cedrela) 

1. Leaf Spots, Downy Mildew — General. Rarely serious. Spots of various sizes, shapes, 
and colors on leaves. Control: None usually necessary. If needed, spray several 
times during wet periods using zineb, maneb, or fixed copper. 

2. Twig Blight, Cankers, Limb Blight — Twigs and branches die back. Discolored 
cankers may form on the twigs causing parts beyond to wilt and die. Control: Cut 
out dead and cankered twigs. If serious enough, spray as for Leaf Spots (above) . 



180 CHINESE BEAUTY BUSH 

3. Powdery Mildew — Grayish-white mold patches on the leaves. Control: None 
usually necessary. If practical, spray once or twice, 10 days apart, using Karathane 
or sulfur. 

4. Black Mildew, Sooty Mold — Black, moldy patches on the leaves following insect 
attacks. Control: Apply malathion sprays to control scales, white flies, and other 
insects. 

5. Wood Rots — See (23) Wood Rot under General Diseases. 

6. Root-knot — See under Peach, and (37) Root-knot under General Diseases. 

7. Mistletoe — See (39) Mistletoe under General Diseases. 

8. Root Rots — See under Apple, and (34) Root Rot under General Diseases. 

9. Thread Blight — Southeastern states. See under Walnut. Control: Spray as for 
Leaf Spots (above) . 

CHINESE BEAUTY BUSH - See Viburnum 

CHINESE BELLFLOWER - See Bellflower 

CHINESE BITTERSWEET - See Bittersweet 

CHINESE CABBAGE -See Cabbage 

CHINESE CEDRELA-See Chinaberry 

CHINESE EVERGREEN - See Calla 

CHINESE FORGET - ME - NOT - See Mertensia 

CHINESE HIBISCUS -See Hollyhock 

CHINESE HOUSES -See Snapdragon 

CHINESE LANTERNPLANT - See Tomato 

CHINESE PARASOLTREE - See Phoenix - tree 

CHINESE PRIMROSE -See Primrose 

CHINESE REDBUD, CHINESE SCHOLARTREE - See Honeylocust 

CHINESE TALLOWTREE - See Castorbean 

CHINESE TRUMPETCREEPER - See Bignonia 

CHINESE WAXGOURD-See Cucumber 

CHINESE WOLFBERRY - See Matrimony - vine 

CHINODOXA - See Tulip 

CHINQUAPIN - See Chestnut 

CHIONANTHUS-See Ash 

CHIVES -See Onion 

CHOKEBERRY, CHRISTMASBERRY - See Apple 

CHRISTMAS CHERRY -See Tomato 

CHRISTMAS - ROSE - See Delphinium 



CHRYSANTHEMUM 181 

CHRYSANTHEMUM [ANEMONE-FLOWERED, ARCTICUM, CUSHION, 

FLORISTS', FOOTBALL MUMS, GARLAND, HARDY, KOREAN, POMPON, and 

TRICOLOR], CORN-MARIGOLD, FEVERFEW, GIANT DAISY, OXEYE DAISY, 

PARIS DAISY or MARGUERITE, PYRETHRUM [ COMMON or PAINTED 

DAISY, DALMATION ] (Chrysanthemum); SNEEZEWORT, YARROW 

(Achillea); YELLOW IRONWEED (Actinomeris); AGERATUM, MISTFLOWER 

(Ageratum); PEARLEVERLASTING (Anaphalis); EVERLASTING, PUSSYTOES 

(Antennaria); CAMOMILE, GOLDEN MARGUERITE (Anthemis); AFRICAN 

DAISY (Arctotis); ARNICA, WORMWOOD [ COMMON, MUGWORT, 
OLDMAN, RUSSIAN, SILVER KING ], DUSTY-MILLER (Artemisia); ASTER 

[ BLUE WOOD, ITALIAN, NEW ENGLAND, NEW YORK, PERENNIAL 

(HARDY ASTER or MICHAELMAS DAISY), ROCK, WHITE HEATH, and 

WHITE UPLAND ] (Aster); BALSAMROOT (Balsamorhiza); ENGLISH DAISY 

(Bellis); BUR -MARIGOLD (Bidens); FALSE - CAMOMILE (Boltonia); SWAN 

RIVER DAISY (Brachycome); POT MARIGOLD (Calendula); CHINA - ASTER 

or ANNUAL ASTER (Callistephus); SAFFLOWER (Carthamus); CORNFLOWER 

or BACHELORS - BUTTON, BASKETFLOWER, DUSTY - MILLER, MOUNTAIN 

BLUET, SWEET SULTAN (Centaurea); GOLDEN - ASTER, ROSINWEED 

(Chrysopsis); THISTLE, PLUMED THISTLE (Cirsium); BLESSEDTHISTLE (Cnicus); 

TICKSEED, GOLDEN - WAVE (Coreopsis); COSMOS [ COMMON, YELLOW ] 

(Cosmos); HAWKSBEARD (Crepis); DAHLIA [ COMMON, MINIATURE, 
POMPON ] (Dahlia); CAPE MARIGOLD (Dimorphotheca); LEOPARDSBANE 

(Doronicum); PURPLE - CONEFLOWER or BLACK SAMPSON (Echinacea); 

GLOBETHISTLE (Echinops); TASSELFLOWER, FLORAS- PAINTBRUSH (Emilia); 

ENCELIA; FLEABANE (Erigeron); BONESET, WHITE SNAKEROOT, 

MISTFLOWER, JOE - PYE - WEED (Eupatorium); BLUE DAISY (Felicia); 

GAILLARDIA, FIREWHEEL or ANNUAL BLANKET - FLOWER (Gaillardia); 

AFRICAN DAISY (Gazania); TRANSVAAL DAISY (Gerbera); SNEEZEWEED, 

YELLOW STAR (Helenium); SUNFLOWER [ASHY, COMMON, DARKEYE, 

GIANT, PRAIRIE, STIFF, THINLEAF ] (Helianthus); STRAWFLOWER 

(Helichrysum); ORANGE SUNFLOWER, OXEYE (Heliopsis); INULA, 

ELECAMPANE (Inula); TIDYTIPS (Layia); BLAZING - STAR, GAYFEATHER, 

BUTTON SNAKEROOT (Liatris); MALACOTHRIX; FALSE - CAMOMILE or 

GERMAN CAMOMILE, TURFING DAISY (Matricaria); STEVIA (Piqueria); 

PRAIRIE -CONEFLOWER (Ratibida); BLACK - EYED - SUSAN, GOLDENGLOW, 

BROWN-EYED - SUSAN, CONEFLOWER (Rudbeckia); Cineraria, DUSTY - 

MILLER, GERMAN IVY, GROUNDSEL, PURPLE RAGWORT (Senecio); 

SILPHIUM, CUP -PLANT or INDIAN - CUP, COMPASSPLANT (Silphuim); 

WIRELETTUCE (Sfephanomeriaj; CORNFLOWER ASTER, STOKES - ASTER 

(Stokesia); MARIGOLD [ AZTEC (AFRICAN or AMERICAN), FRENCH, 

GUINEA GOLD ] (Tagetes); TANSY (Tanacetum); TORCH FLOWER (Tithonia); 

COLTSFOOT (Tussilago); CROWNBEARD (Verbesina); WYETHIA; ZINNIA 

l.Leaf Spots, Leaf Blight or B lo tch — General. May be serious. Spots of various 
shapes, sizes, and colors on the leaves. Spots may run together forming large, ir- 
regular blotches. Leaves may discolor, gradually wither, and die. Often starts at 
base of plant and progresses upward. Leaves may drop early or cling to the stem. 
Certain spots also occur on the stems and flower petals. See Figure 94. Control: 
Burn tops in the fall. Rotate. Keep down weeds. If practical, pick off and burn 
the first infected leaves. Apply zineb, ferbam, maneb, thiram, captan, or phaltan 
at 7- to 10-day intervals during wet weather. Dip cuttings in a solution of ferbam, 
captan, zineb, ziram, or thiram (\\/ 2 tablespoons per gallon) before sticking in the 
rooting medium. Soak China-aster seed for 30 minutes in a 1:1,000 solution of 





Fig. 94B. Septoria leaf spot and blight 
of chrysanthemum. 



Fig. 94A. Alternaria blight of zinnia. 




Fig. 95. Chrysanthemum powdery mildew. 



CHRYSANTHEMUM 



183 



mercuric chloride or Semesan (2 teaspoons per quart) then wash (after mercuric 
chloride treatment) thoroughly in running water for 5 minutes, dry, and plant. 
Soak zinnia seed in hot water (125° F.) for 30 minutes then dry and treat seed 
with captan, thiram, or chloranil. Treat other seed by dusting with captan, thiram, 
or chloranil. See "Seed Treatment Methods and Materials" in the Appendix. Varie- 
ties of certain plants (e.g., chrysanthemum and zinnia) differ in susceptibility. In- 
doors, keep water off the foliage. Do not work among wet plants. 
Poivdery Mildeivs — General. Powdery, whitish, mold patches on leaves, stems, and 
flower buds especially in late summer. Mostly on the lower half of infected plants. 
Leaves may wither and drop prematurely. Plants may be stunted, disfigured, and 
weakened. See Figure 21A under General Diseases and Figur 95. Control: Avoid 
overcrowding. Collect and burn tops in the fall or after harvest. Resistant varieties 
are available for some plants. Apply Karathane, phaltan, sulfur, or Acti-dione fol- 
lowing the manufacturer's directions. Avoid dusting or spraying when tempera- 
tures are above 85° F. 

Crown, Stem and Root Rots, Southern Blight, Cutting Rot, D ampin g-off — Gen- 
eral. May be serious in wet weather. Plants often stunted and sickly. Foliage wilts 
and turns yellow. Plants suddenly or gradually die. May collapse. Near the soil 
line the stem may be water-soaked or discolored, brown, bleached white, black or 
covered with a cottony mold. Roots (and tuber) decayed or may rot in storage. 
Common on heavy, wet soils. Seedlings wilt and collapse (damp-off) . See Figure 
37A, (21) Crown Rot, and (34) Root Rot under General Diseases. Often associ- 
ated with root-feeding nematodes. Control: Dig up and destroy infected plants. 
Take tip cuttings from vigorous, disease-free plants and plant in a sterilized root- 
ing medium (pages 437-44) . Plant in well-drained soil in a sunny location. Five- 
year rotation. Grow resistant varieties, if available. Avoid overcrowding, over- 
watering, overstimulation with fertilizer and planting in infested soil. Spot drench 
with Terraclor 75 per cent (PCNB) and captan 50 per cent or ferbam 76 per cent, 
when crown rot is first evident. See under Wirestem of Cabbage. Plant disease-free 
seed treated with captan, thiram, or chloranil. See Table 13 in the Appendix. 
Aster Yellows, Stunt — General and serious. Symptoms variable. Leaves yellowish. 
Plants often stiff, stunted or dwarfed, and "bushy" with numerous, yellowish, up- 
right, spindly shoots. Leaves are often mottled and distorted. Older leaves may 



HEALTHY 



DISEASED 



Fig. 96. Aster yellows of marigold. 




be reddish. Flowers may be deformed and greenish, dwarfed, or none. Bloom 
may be greatly reduced, especially in future years. Infected plants never recover. 
See figures 34A and D under General Diseases and Figure 96. Control: Grow 
plants under fine cheesecloth (22 threads per inch) , wire (18 wires per inch) , 
or apply insecticide (e.g., DDT and malathion) at least weekly. This controls the 
leafhoppers which transmit the virus. Destroy the first infected plants. Keep down 



184 CHRYSANTHEMUM 

all weeds within 200 feet of flower beds, if possible. Plant virus-free stock from a 
reputable nursery. 

5. Mosaics, Dwarf, Stunt, Leaf Curl, Rosettes — General. A virus complex. Plants of- 
ten stunted or dwarfed and "bushy" with curled, dwarfed, distorted, mottled, yel- 
low, and light or dark green leaves. Bloom may be greatly reduced, especially in 
future years. Infected plants never recover. Flowers often stunted. May show 
streaks or develop distorted petals. Symptoms may be masked in hot weather or 
are never expressed in certain varieties. See (16) Mosaic, and (18) Yellows 
(Stunt) under General Diseases. Control: Remove and burn infected plants when 
first seen. Plant virus-free seed and transplants or propagate only from known 
disease-free plants. Keep down weeds. Control aphids and leafhoppers which 
transmit the viruses using DDT or methoxychlor and malathion. 

6. Ringspot, Oakleaf Disease (primarily aster, calendula, China-aster, dahlia, straw- 
flower, sunflower, and zinnia) — Irregular, pale green to bright yellow or yellowish- 
green spots, single or zoned rings, oakleaf or irregular zigzag markings, and other 
line patterns on the leaves. See Figure 33B under General Diseases. Leaves may 
tend to outgrow symptoms. Control: Same as for Mosaics (above) . 

7. Spotted Wilt, Ringspot — Symptoms variable. Pale yellow to dark green spots, ring 
or line patterns develop in the leaves. Leaves may later be distorted or appear 
bronzed, often with a slight mottling. Dead areas may appear in the leaves and 
stem. Young plants are commonly killed. Flowers are often dwarfed and dis- 
torted. See (17) Spotted Wilt under General Diseases. Control: Same as for Mo- 
saics (above) . Control thrips and aphids which transmit the virus. Use a mixture 
of DDT and malathion. 

8. Curly-top — Plants "bushy" with shoot lips turning yellow. Leaflets often curled 
and twisted with petioles turning down. Flower buds and flowers are dwarfed. 
See Figure 35B. Control: Same as for Aster Yellows (above) . 

9. Fusarium Wilt, Stem Rot — General and serious on China-aster and marigold. 
Symptoms variable. Plants may wilt and gradually or suddenly wither and die at 
any age. Stem may be water-soaked or darkened near the soil line. Plants often 
stunted, yellowish, and show one-sided growth. Young plants suddenly wilt and 
die. See Figure 29D under General Diseases. Control: Grow wilt-resistant varieties 
of China-aster and African marigold. Plant disease-free seed or plants in clean or 
sterilized soil (see "Soil Treatment Methods and Materials" in the Appendix) or 
soak China-aster seed for 30 minutes in a 1:1,000 solution of mercuric chloride. 
Then wash thoroughly for 5 minutes in running water, dry at room temperature, 
and dust with thiram, chloranil, or captan. Five to 6-year rotation. Plant in well- 
drained, disease-free soil where wilt has not been a problem. 

10. V erticillium Wilt — Widespread. Symptoms variable. Whole plant may be stunted 
with pale green to yellow leaves. Leaves wilt, wither, die, and cling to the stem, 
starting usually at the base. Often starts on one side of the plant. Plants may 
ripen prematurely. Shoot tips may be blighted. Dark streaks occur inside the 
lower stem. Chrysanthemum varieties differ in resistance. See under Bellflower, 
and (15B) Verticillium Wilt under General Diseases. Control: Dig up and burn 
infected plants. Otherwise same as for Fusarium Wilt (above) . Cultured cuttings 
of chrysanthemum are available. 

11. Bacterial Wilt — Mostly southern states or in greenhouses. Plants suddenly wilt 
and collapse. "Recover" at night for a few days before plants dry up and die. 
Usually there is a soft, wet rot inside the stem near the soil line. Control: Plant 
disease-free seed in clean or sterilized soil or cuttings from healthy plants. Dig up 
and burn infected plants. 

12. Rusts— General. Small, bright orange, yellowish-orange, reddish-brown or chocolate- 



CHRYSANTHEMUM 



185 



Fig. 97. Chrysanthemum rust. 




brown, dusty pustules mostly on the underside of leaves. Leaves may turn yellow, 
wither, and die. If severe, plants may be stunted. Alternate hosts may include 
pines, sedges, rushes, and wild grasses. See Figure 97. Control: If practical, pick 
off and burn infected leaves. Burn tops in the fall or plow them under cleanly. 
Take cuttings from healthy plants. Destroy alternate hosts where feasible. Indoors 
avoid sprinkling foliage. Keep the humidity down and increase air circulation. 
Apply zineb, ferbam, thiram, maneb, or sulfur at 7- to 14-day intervals during wet 
periods, starting in early summer. Resistant varieties of China-aster and possibly 
other plants are available. Treat saff lower seed with Panogen 15 or Ceresan and 
store seed, if possible, for 1 to 2 months or longer before planting. Acti-dione (1 
to 20 parts per million) as a 30-minute soak or a dichlone dust are also recom- 
mended. 

13. Gray-mold Blight, Botrytis Blight, Head or Blossom Blights, Ray Blight, Stem 
Blight, Bud Rot — Cosmopolitan. Small to large, water-soaked to tan or brown spots 
on flower petals, leaves, buds, and stems. Stems (cuttings) may rot causing the 
foliage beyond to wilt, wither, and die. Affected parts may be covered with a 
coarse, tannish-gray mold in damp weather. Seedlings wilt and collapse. Common 
on fading flower heads. Flowers may be deformed, one-sided, or blasted. Buds 
may rot. See Figure 19D and Figure 45D under General Diseases. Control: Destroy 
fading flower heads promptly. Space plants and keep down weeds. Avoid over- 
watering and forcing plants too rapidly. Indoors, same as for Rusts (above) . 
Spray buds and blooms lightly with zineb or captan. Apply maneb, zineb, ferbam, 
dichlone, or captan, plus wetting agent, at weekly intervals during wet weather. 
Spot drench with Terraclor 75 per cent (PCNB) just before planting. 

14. Stem Cankers — Cankers form on the stem near the ground line or where branches 
arise. Roots and crown are usually healthy. Control: Keep base of plants dry. 
Spray as for Leaf Spots and Rusts (both above) . Burn tops in the fall. Destroy in- 
fected plants when found. 

15. Root-knot — See under Bean, and Figure 50 under General Diseases. Calendula is 
highly susceptible. 

16. Downy Mildews — Widespread. Pale green or light yellow spots or mottling on the 
upper leaf surface with a delicate, whitish mold on corresponding underleaf sur- 
face. Leaves shrivel and die. Seedlings may wilt and die. Control: Same as for Gray- 
mold Blight (above) . 

17. Leaf or Leaf Gall Nematodes (aster, balsamroot, chrysanthemum, dahlia, ground- 
sel, wyethia, zinnia) —Widespread and serious on chrysanthemum in wet sea- 
sons. Wedge-shaped to irregular, yellowish-brown to gray areas in leaves, bounded 
by the larger veins. Blotches later turn brown to black, enlarge, and run to- 
gether. Leaves wither, die, and hang downward on the stem starting at the base. 
Plants lack vigor. May die prematurely. Flowers develop improperly. Varieties 



186 CHRYSOPSIS 

differ in resistance. Plants stunted in early spring with dwarfed, distorted, and 
crinkled leaves. See Figure 36A under General Diseases. Control: Take cuttings 
from the tips of tall, disease-free plants. Burn all tops and fallen leaves in autumn. 
Pick off and burn infested leaves and the two healthy-appearing leaves above, as 
they develop. Mulch plants to avoid splashing water on the foliage. Rotate. Do 
not propagate from infested clumps. Avoid overhead watering. Nurserymen soak 
dormant chrysanthemum stock plants (or "stools") in hot water (118° F.) for 15 
minutes or 112° F. for 30 minutes. The treatment is often injurious. 

18. Crown Gall — Plants stunted with spindling shoots. Large, gall-like tumors at 
base of plant, on the roots or both places. Control: See (30) Crown Gall under 
General Diseases. Pull up and burn affected plants. 

19. Storage Rots (dahlia) —See under Carrot. Do not dig until tubers are mature, 
but before frost injury occurs. Store only sound, thoroughly dried tubers in a 
dry, cool (40° F.) location. 

20. White or Leaf Smuts (arnica, aster, boltonia, calendula, dahlia, fleabane, gaillardia, 
prairie coneflower, rudbeckia, senecio, silphium, sneezeweed, sunflower) — Round 
to irregular, yellowish-green spots which later turn brownish to black. Spots may 
drop out leaving shot-holes. Leaves may drop early. See (13) White Smut under 
General Diseases. Indoors, keep water off the foliage. 

21. White-rust — Pale yellowish spots on the leaves which later turn brown. Snow- 
white, powdery pustules develop on the lower leaf surface. Leaves may die. Plants 
are often dwarfed. Control: Collect and burn infected plant parts and destroy 
all plant debris after harvest. Keep down weeds. See also (9) White-rust under 
General Diseases. 

22. Fasciation, Leafy Gall (primarily chrysanthemum, dahlia, piqueria, pyrethrum, 
and Shasta daisy) — Mass of stems, shortened and thick with cauliflowerlike growth 
at the soil line. Leaves aborted and misshapen. Plants dwarfed with abundant 
buds and distorted shoots. Clumps may rot. Control: See (28) Leafy Gall under 
General Diseases. 

23. Bacterial Blight (chrysanthemum) —Water-soaked to brown or reddish-brown, 
rotted spots on the stem which may extend down to the soil line. Stems may col- 
lapse. Cuttings rot at the base. Control: Snap off cuttings from healthy plants. 
Plant in sterilized soil to which streptomycin (10 parts per million) is added. 

24. Black Mold — Sootlike patches on the foliage. See (12) Sooty Mold under General 
Diseases. 

25. Scab (dahlia, tickseed) —See under Beet, and (14) Scab under General Diseases. 

26. Dodder — See Figure 53 under General Diseases. 

27. 2,4-D Injury — See under Grape. 

28. Other Root-feeding Nematodes (bulb, dagger, lance, pin, ring, root-lesion or 
meadow, spiral, stubby-root, stylet) — Associated with stunted, sickly plants. Roots 
may be short, stubby, discolored and decayed. Control: See under Root-knot 
(above) . 

29. Hopperburn (primarily dahlia) — See under Potato. Leaf margins are scorched. 
Plants may be stunted and yellowish. 

CHRYSOPSIS — See Chrysanthemum 

CHUPEROSA-See Clockvine 

CICHORIUM-See Lettuce 

CIGARFLOWER, FIRECRACKER PLANT (Cuphea) 



CITRUS 187 



1. Gray-mold B ligh t — Occasional in greenhouses. See under Begonia, and (5) 
Botrytis Blight under General Diseases. 

2. Powdery Mildew — See (7) Powdery Mildew under General Diseases. 

3. Root Rot — See under Geranium, and (34) Root Rot under General Diseases. 

4. Root-knot — See (37) Root-knot under General Diseases. 

5. Leaf Spot — See (1) Fungus Leaf Spot under General Diseases. 

CIMICIFUGA — See Anemone 

CINCHONA - See Buttonbush 

CINERARIA — See Chrysanthemum 

CINNAMON - TREE (Cinnamomum) — See Avocado 

CINNAMONVINE-See Yam 

CINQUEFOIL-See Rose 

CIRSIUM — See Chrysanthemum 

CISSUS-See Grape 

CITRON — See Cucumber 

CITRUS: LEMON [ PONDEROSA, MEYER, LIME], ORANGE [SOUR or 

SEVILLE, KING, OTAHEITE, SATSUMA, MANDARIN, COMMON or SWEET], 

GRAPEFRUIT, PUMMELO, TANGERINE, TANGELO (Citrus); KUMQUAT 

(Fortunella); HARDY or ORIENTAL ORANGE (Poncirus) 

1. Root Rots, Collar or Foot Rot, Tree Decline — See under Apple, Dogwood, and 
(34) Root Rot under General Diseases. Seedlings may wither and die. Often 

associated with nematodes (e.g., burrowing, citrus, dagger, lance, reniform, ring, 
root-knot, root-lesion or meadow, sheath, sheathoid, spiral, sting, stubby-root) . 
Control: Plant in sterilized soil (pages 437-44) . Avoid overwatering. Commercial 
growers soak bare-rooted nursery stock in hot water (122° F.) for 10 minutes be- 
fore planting. 

2. Chlorosis, Leaf Yellowing — Leaves turn yellowish-green or remain green along 
the veins. May fall early. Plants stunted and sickly. See also under Gardenia. 
Control: Plant in slightly acid (pH 6.5) soil which is sterilized and well-drained. 
Avoid overwatering, overfertilizing, adding excess lime, and great temperature 
changes. Repot if roots are potbound. Control insects and mites by using malathion. 
Place in a sunny location. 

3. Leaf Spot, Anthracnoses, Wither Tip, Twig Blight — General. Leaves are spotted. 
Shoots and twigs may wither and die back. Gum may exude from wounds. Buds 
may not open and often drop. Control: Indoors, keep water off the foliage. Keep 
trees growing vigorously by proper fertilization and watering, and controlling in- 
sects with malathion sprays. Pick or prune off and burn blighted parts. Outdoors, 
spray during rainy periods using zineb, ferbam, maneb, or captan. 

4. Sooty Molds, Sooty Blotch — Black mold patches on leaves, twigs, and fruits fol- 
lowing attacks by aphids, scales, mealybugs, whiteflies, and other insects. Control: 
Apply malathion sprays to control insects. 

5. Crown Gall — See under Apple, and (30) Crown Gall under General Diseases. 

6. Other Diseases — If grown outdoors, in citrus-growing areas, many other diseases 
could occur. Check with your county agent or extension plant pathologist. Excel- 



188 CLADRASTIS 

lent bulletins, e.g., Handbook of Citrus Diseases in Florida, Florida Agricultural 
Experiment Station Bulletin 587, are also available. 

CLADRASTIS - See Honeylocust 

CLARKIA-See Fuchsia 

CLEMATIS [HENRY, JACKMAN, JAPANESE], VIRGINS - BOWER (Clematis); 
YELLOWROOT, SHRUB- YELLOWROOT (Xanthorhiza) 

1. Leaf Spots, Leaf B Ugh t — Widespread. Tan, gray, reddish-brown, or brown spots 
of various sizes and shapes on leaves. Leaves may wither and drop early. Control: 
If practical, remove and burn infected leaves. Space vines. Plant in a new location. 
Apply zineb, ferbam, captan, maneb, thiram, or fixed copper at 7- to 10-day in- 
tervals during wet weather. 

2. Stem Rot, Wilt (clematis) — Foliage wilts, withers, and dies from a girdling dark 
canker on the stem near the soil line. Roots may decay. Control: Same as for Leaf 
Spots. Plant in well-drained soil. Drench soil with zineb or thiram (2 tablespoons 
per gallon) when disease is first noticed. Repeat weekly for a month. 

3. Powdery Mildews — Widespread. Powdery, white mold growth on clematis foliage. 
Sometimes on flower petals. Large-flowered varieties appear more susceptible. 
Control: Spray two or three times using Kara thane. 

4. Root-knot — Clematis is very susceptible. Plants are stunted and sickly with small 
galls formed on the roots. Control: Plant disease-free plants in clean or sterilized 
soil (pages 437-44) . 

5. Rusts (clematis) — Small, yellowish spots on leaves. Alternate hosts include many 
native grasses. Control: Same as for Leaf Spots (above) . 

6. Crown Gall (clematis) — See (30) Crown Gall under General Diseases. 
I.Mosaic (clematis) —See (16) Mosaic under General Diseases. 
S.Smut (clematis) —See (11) Smut under General Diseases. 

9. Other Root-feeding Nematodes (e.g., dagger, root-lesion, spiral, stylet or stunt) . 
Often associated with sickly, stunted plants. Control: Same as for Root-knot 
(above) . 

CLEOME — See Spiderflower 

CLERODENDRON-See Lantana 

CLETHRA — See Sweet - pepperbush 

CLIFFGREEN - See Bittersweet 

CLIFTONIA - See Buckwheat-tree 

CLIMBING MIGNONETTE -See Lythrum 

CLINOPODIUM-See Salvia 

CLITORIA-See Pea 

CLOCKVINE (Thunbergia); CHUPEROSA (Beloperone); DYSCHORISTE; 
ERANTHEMUM; RUELLIA; SANCHEZIA 

l.Leaf Spots — Spots of various sizes, shapes, and colors on the leaves. Control: Pick 
off and burn spotted leaves. If practical, spray during rainy periods using ferbam 
or zineb. 

2. Rusts (chuperosa, dyschoriste, ruellia) — Yellow, orange-yellow, reddish-brown or 
black, powdery pustules on the leaves. Control: Same as for Leaf Spots. 



COLCHICUM 189 



3. Crown Gall — Rough, swollen galls form at or near the soil line. See (30) Crown 
Gall under General Diseases. 

4. Oedema (eranthemum) —Indoor problem. "Sandy," rust-colored, swollen spots. 
Mostly on the upper leaf surface. Control: Avoid overwatering in overcast, damp 
weather. Increase air circulation. 

5. Root-knot — See (37) Root-knot under General Diseases. 

6. Aster Yellows — See (18) Aster Yellows under General Diseases. 

7. Root Rot — See (34) Root Rot under General Diseases. May be associated with 
root-feeding nematodes (e.g., burrowing) . 

CLOUDBERRY - See Raspberry 

CNICUS — See Chrysanthemum 

COCCULUS-See Moonseed 

COCHLEARIA - See Cabbage 

COCKSCOMB (Celosia); GLOBE-AMARANTH (Gonwhrena); AMARANTH, 

LOVE-LIES-BLEEDING, JOSEPHSCOAT, PRINCESFEATHER (Amaranthus); 

ALTERNANTHERA; BLOODLEAF (Iresine); FROELICHIA 

1. Seed Rot, Damping-off, Blight — Seeds rot. Seedlings wilt and collapse from water- 
soaked, blackish-brown spots or rot near the soil line. Older plants show rusty- 
brown, zoned spots on the leaves, petioles, and stems. Spots dry out and become 
cankers. Control: See under Beet. Pull up and burn badly infected plants. Avoid 
overwatering. Rotate or plant in sterilized soil (see pages 437-44) . 

2. Leaf Spots, Leaf Blight — Spots of various sizes, shapes, and colors on the leaves. 
Leaves may curl up and fall early. Control: See under Chrysanthemum. 

3. Curly-top, Yellows — See under Beet, and (18) Yellows and (19) Curly-top under 
General Diseases. Plants are stunted and yellowed. 

4. Root-knot — See (37) Root-knot under General Diseases. 

5. White-rust (amaranth, froelichia, globe-amaranth) — White, powdery spots on 
the leaves which turn reddish-brown at maturity. Flowers and stems may be 
stunted and distorted. Control: See under Chrysanthemum. 

6. Leaf Roll (cockscomb, amaranth) — See under Potato. 

7. Black Ringspot (cockscomb) — See under Cabbage. 

8. Root and Crown Rots (alternanthera, bloodleaf, cockscomb) — Cuttings and young 
plants are stunted, often wilt and die. Roots and crowns are decayed. Control: 
Plant in sterilized soil, or treat the soil with Terraclor (PCNB) before planting. 

9. Fusarium Wilt (alternanthera) — See under Chrysanthemum. 

10. Inflorescence Smut (bloodleaf) —See (11) Smut under General Diseases. 

11. Blossom Blight (amaranth) —See (31) Flower Blight under General Diseases. 

12. Other Root-feeding Nematodes (e.g., pin, root-lesion, spiral) —Associated with 
sickly, stunted plants. Control: Same as for Root-knot (above) . 

COCONUT (Cocos;-See Palms 

CODIAEUM-See Croton 

COFFEEBERRY - See Buckthorn 

COLCHICUM, AUTUMN-CROCUS (Colchicum); CAMASS (Camassia) 

1. Smut — Small, swollen "blisters" (spots or stripes) on leaves, corms, stems, and 
flowers. Blisters are filled with black, powdery masses. Varieties differ in resistance. 
Control: Pick off and burn affected plant parts before blisters break open. 



190 COLEUS 

2. Corm (Bulb) Rots — See under Tulip. Corms rot in the field or storage. 

3. Botrytis Leaf Spot and Tip Blight — See under Tulip, and (5) Botrytis Blight 
under General Diseases. 

4. Leaf Spot — Small spots on the leaves. Control: Same as for Botrytis Leaf Spot. 

COLEUS -See Salvia 

COLLINSIA - See Snapdragon 

COLLOMIA - See Phlox 

COLTSFOOT — See Chrysanthemum 

COLUMBINE - See Delphinium 

COLUMBO-See Gentian 

COLUTEA - See Honeylocust 

COMMELINA — See Tradescantia 

COMPASSPLANT - See Chrysanthemum 

COMPTONIA — See Sweetfern 

CONEFLOWER - See Chrysanthemum 

CONFEDERATE - JASMINE - See Oleander 

CONVALLARIA - See Lily 

CONVOLVULUS -See Morning-glory 

COOPERIA-See Daffodil 

COPPERLEAF - See Acalypha 

COPPER - TIP - See Gladiolus 

COPTIS — See Delphinium 

CORALBEAN, CORAL - TREE - See Honeylocust 

CORALBELLS - See Hydrangea 

CORALBERRY- See Snowberry 

CORDYLINE - See Dracaena 

COREOPSIS — See Chrysanthemum 

CORIANDER (Cordiandrum) — See Celery 

CORONILLA - See Pea 

CORN [ BROOM, ORNAMENTAL or INDIAN, POP, SWEET ] (lea) 

1 . Bacterial Wilt, Stewart's Disease — General. May be serious. Most severe in north- 
ern states following mild winters. Long, yellowish or pale green streaks or spots 
in leaves which later turn brown. Seedlings or older plants often stunted, wilt, 
and die. Plants often tassel prematurely. Leaves dry out and appear as if frosted. 
Sweet corn and popcorn are quite susceptible. See Figure 31 A under General 



CORN 



191 



Fig. 98. Bacterial wilt of corn. 




Diseases and Figure 98. Control: Plant disease-free seed. Spray with DDT or diel- 
drin at regular intervals, starting when the corn emerges, to control flea beetles 
which transmit the wilt-producing bacterium. Check with your county agent or 
extension entomologist regarding timing of sprays for your area. More or less 
tolerant sweet corn varieties: Calumet, Carmelcross, Country Gentleman W-R, 
Early Gold Crest, F-M Cross, Golden Beauty, Golden Cross W-R, Golden 22, 25, 
50, etc., Golden Harvest, Golden Pirate, Goldrush, Honeycross, Ioana, Iochief, Mar- 
cross, Seneca, Seneca Dawn, Tendermost, and many more. Somewhat resistant pop- 
corn varieties: South American and Sunburst. 

2. Smuts — General, especially following hail or insect injury. Small to large, silvery- 
white galls or "boils" on tassel, ears, husks, leaves, prop roots, or stalk. Mem- 
brane breaks releasing dark brown to black, sooty masses. Stalks may be barren. 
Sweet corn is very susceptible. See Figure 25A under General Diseases. Control: 
Cut out and burn galls before they break open. Rotate. Control insects (e.g., corn 
earworm and European corn borer) by DDT sprays. Check with your county 
agent for correct timing. Partially resistant sweet corn varieties: Asgrow Golden 
60, Country Gentleman, Evertender, Giant Bantam Hybrid, Golden Cross Bantam 
Hybrid, Golden Hybrid 2057, Ioana, Iochief, Mellow Gold, Pennlewis, Pros- 
pector, Seneca Brave, Tenderblonde, and Victory Golden. Differences also exist 
between popcorn hybrids. 

3. Root and Stalk Rots — General. Plants often lean, break, or blow over. May die 
prematurely. Plants may be stunted, lack vigor. Stalks weak, rotted internally at 
base. Both fine and larger roots decay. Often associated with nematodes. When 
severe, plants may wither and die prematurely, producing poorly filled or nubbin 
ears. Excessive nitrogen fertilizer increases stalk breakage. See Figure 99. Control: 
Treat seed as for Seed Rot (below) . Plant in fertile, well-drained soil. Maintain 
balanced soil fertility which is based on a soil test. Avoid excessively deep and 
close cultivations. Use locally adapted, resistant hybrids whenever available. Con- 
trol soil insects, using aldrin, chlordane, dieldrin, or heptachlor. Apply to the 




Fig. 99. Stalk rot of corn. 



soil surface before planting and work into the top 6 inches. Follow the manufac- 
turer's instructions. Repeat every 4 years. 

4. Ear and Kernel Rots — Cosmopolitan. Ears and husks may be completely rotted 
and discolored white, gray, blue, pink to reddish, or black. Plants may be stunted. 
Often associated with Root and Stalk Rots. Rotted shanks and ears may break 
over early. Control: Same as for Root and Stalk Rots (above) . In addition, handle 
carefully at harvest. Control corn earworms by DDT sprayed into the silks. Check 
with your county agent or extension entomologist. 

5. Seed Rot, Seedling Blights — General. Seeds rot. Stand is poor, especially during 
cold, wet weather. Growth is uneven. Seedlings are yellow, stunted, may wilt and 
die. Control: Plant seed treated with captan, thiram, chloranil, or dichlone plus an 
insecticide (e.g., dieldrin or lindane) . See Table 13 in the Appendix. Plant mature, 
high-quality, crack-free seed in warm, well-drained soil. Treat for soil insects as 
given under Root and Stalk Rots (above) . 

6. Helminthosporium Leaf B Ugh ts — Widespread. Small to large, grayish-green to 
tan or brown spots (often elliptically-shaped) on the lower leaves from midsum- 
mer on. Later the upper leaves may become infected. Plants often appear as if suf- 




Fig. 100. Helminthosporium (northern) 
leaf blight of corn. 



CORN 



193 



fering from drought or frost. See Figure 100. Control: Hybrids show differences. 
Often practical to spray sweet corn in very humid areas (e.g., the Gulf Coast) , 
using zineb or maneb plus a spreader-sticker at about weekly intervals. Thorough 
coverage is essential. Plant early, using disease-free seed. Treat seed as for Seed Rot 
(above) . Three-year rotation. Burn or bury deeply all plant debris after harvest. 
Avoid overhead sprinkling and poorly drained soil. Sweet corn varieties differ in 
resistance. 

7. Leaf Rusts— General. Small, yellow-orange to reddish-brown or cinnamon-brown, 
powdery pustules on the leaves which finally turn black in color. If numerous, 
leaves may die early. Alternate host of Common Corn Rust is wood sorrel (Oxalis) . 
Sweet corn varieties differ in resistance. Control: None usually needed. Spraying 
as for Helminthosporium Leaf Blights may be beneficial. Resistant sweet corn va- 
rieties: Country Gentleman and Crosby. Popcorn is usually resistant. 

8. Bacterial Leaf Blights and Stalk Rot — Small, tan to dark brown spots to long 
narrow stripes on leaves following showery weather. Spots may run together to 
form irregular blotches. Stalk may suddenly rot and collapse. Control: None usually 
necessary. Seed treatment as for Seed Rot (above) . Hybrids offer some hope. 



Fig. 101. Crazy top of corn. 




9. Crazy Top — Uncommon. Tassel composed of a large mass of short leaves. Plants 
are stunted, tiller excessively, and have narrow leaves. Stalks are barren. See Fig- 
ure 101. Control: Avoid planting in low, wet spots which are likely to be flooded 
after seeding. Or drain such areas. 

10. Black Bundle — Stalks and leaves are reddish-purple. Stalks often barren or pro- 
duce small, poorly-filled ears. Black streaks inside stalk. Plants often tiller ex- 
cessively. Control: None known. 

11. Minor Leaf Spots — Mostly southern states. Small, round to elongate, light green, 
gray, tan to yellow or dark brown spots, blotches, or streaks on leaves and leaf 
sheaths. Spots may run together forming irregular blotches. Infected stalks break 
easily. Control: Same as for Helminthosporium Leaf Blights (above) . 

12. Purple Sheath Spot — Irregular, purple blotches on leaf sheaths. Control: Hybrids 
and varieties differ in resistance. 

13. Sweet Corn Mosaics and False-stripe, Leaf Fleck, Corn Stunt — Many small, broken, 
yellowish or bleached flecks, spots, and streaks on leaves parallel with the veins. 
Plants may be dwarfed, pale yellow; leaves split. Others show new leaves almost 
free of stripes. Control: None known. Resistant hybrids may be available in the 
future. Aphids or leafhoppers may transmit the viruses. 



194 CORNCOCKLE 

14. Stunt — Plants stunted and bushy with yellowish-white and green leaves with a 
broad, bronze-red band running the length of the leaves. Many secondary shoots 
are formed in the axils of leaves. Virus is spread by leafhoppers. Control: None 
known. 

15. Witchweed (Striga) —Southeastern United States in light, sandy soils. Caused by 
a small, parasitic flowering plant (Striga) . Corn plants are severely stunted, yel- 
lowed. Wilt severely. Eventually the leaves turn brown and the plant dies. Striga 
feeds on the roots of corn and related grassy plants. Witchweed plants rarely grow 
over 8 to 9 inches tall, with brick-red, yellowish-red, yellow or white flowers. The 
leaves are light to dark green and slightly hairy. Control: If you suspect Witchweed, 
check with your county agent, extension weed specialist, or plant pathologist. 
Apply 2,4-D, where practical, before plants produce seeds. Fenac, a new preplant- 
ing herbicide, may be recommended. 

16. Root Nematodes (awl, burrowing, dagger, lance, needle, pin, reniform, ring, root- 
lesion or meadow, sheath, sting, stubby-root, stylet or stunt) — Most serious in 
southern states. Symptoms variable. Plants may be stunted and unthrifty. Do not 
respond normally to water and fertilization. Often discolored and may be con- 
fused with one or more deficiency diseases. Roots often stunted (stubby) , may 
be "bushy," show dark spots, witches'-brooms, or galls. 

17. Chlorosis — Deficiency of magnesium, manganese, zinc, or copper. See pages 17-18. 

CORNCOCKLE -See Carnation 

CORNEL, CORNELIAN CHERRY - See Dogwood 

CORNFLOWER, CORNFLOWER ASTER, CORN-MARIGOLD - 
See Chrysanthemum 

CORNSALAD - See Valerian 

CORNUS — See Dogwood 

CORYDALIS - See Bleedingheart 

CORYLUS-See Birch 

COSMOS — See Chrysanthemum 

COTINUS-See Sumac 

COTONEASTER-See Apple 

COTTON - ROSE - See Hollyhock 

COTTONWOOD - See Poplar 

COWSLIP -See Primrose 

CRABAPPLE - See Apple 

CRAMBE-See Cabbage 

CRANBERRY, CRANBERRY - BUSH - See Viburnum 

CRANESBILL, GERANIUM [BLOOD - RED, CAROLINA, SPOTTED or WILD], 
HERB ROBERT or RED - ROBIN (Geranium); HERONSBILL (Erodium) 

1. Fungus Leaf Spots — Spots of various sizes, shapes, and colors on leaves. Control: 
Pick off and destroy spotted leaves. If serious enough, spray several times, 10 to 
14 days apart, during wet periods. Use captan, zineb, or maneb. 



CREPIS 195 



2. Bacterial Leaf Spots — Small, round to angular, reddish-brown to black spots 
with colorless or water-soaked borders form on leaves. Centers of spots later turn 
dry and resemble "frog-eyes." Young leaves may wither and drop off. Petioles 
may also be spotted. Control: Pick off and burn infected leaves. Where practical, 
keep water off the leaves. Space plants. 

3. Mosaic (geranium) — Plants stunted with mottled and distorted leaves. Control: 
Destroy infected plants when first seen. Keep down weeds. Spray or dust to con- 
trol aphids which transmit the virus. Use lindane or malathion. 

4. Rusts (geranium) — See under Chrysanthemum. Alternate host: Polygonum spp. 
or none. 

5. Downy Mildew — Widespread. See (6) Downy Mildew under General Diseases. 

6. Botrytis Leaf Spot, Stem Rot — See (5) Botrytis Blight under General Diseases. 

7. Stem, Crown, Root and Rhizome Rots — See Root Rot under Geranium. May be 
associated with root-feeding nematodes (e.g., lance, pin, root-knot, root-lesion, 
spiral, stem, stubby-root, stylet or stunt) . 

8. Aster Yellows (heronsbill) —See (18) Yellows under General Diseases. 

9. Curly-top (heronsbill) —See (19) Curly-top under General Diseases. 

10. Powdery Mildews (geranium) —See (7) Powdery Mildew under General Diseases. 

11. Root-knot — See (37) Root-knot under General Diseases. 

CRAPE-JASMINE - See Oleander 
CRAPEMYRTLE (Lagerstroemia) 

1 . Powdery Mildews — Widespread and serious during spring and fall. Leaves and 
young shoots may be heavily coated with a powdery, white mold. Shoots, leaves, 
and flowers may later be distorted and stunted. Flower buds may not open. In- 
fected leaves and buds often drop early. Control: Apply Karathane, phaltan, or 
sulfur at 10-day intervals until mildew is checked. Or use Acti-dione following 
the manufacturer's directions. Start when mildew is first seen. Another control is 
to apply lime-sulfur (diluted 1 to 80 with water) as the buds break open. Repeat 
two weeks later. 

2. Leaf Spots, Black Spot, Tip Blight — Leaves spotted. If severe, leaves may wither 
and drop early. Control: If practical, apply two or three sprays or dusts of zineb 
or maneb 10 days apart. 

3. Sooty Mold — Black, sootlike blotches on foliage following attacks by aphids or 
scale insects. Control: Apply malathion to control insects. 

4. Root Rot — See (34) Root Rot under General Diseases. 

5. Chlorosis — Plants sickly and yellowish. Control: Fertilize plants adequately. Be 
sure soil is not too acid or alkaline, but near neutral (pH 6.5 to pH 7.2) . 

6. Thread Blight — Southeastern states. See under Walnut. Plants may be defoliated 
early. 

7. Root-knot — See (37) Root-knot under General Diseases. 

CRASSULA-See Sedum 

CRATAEGUS - See Apple 

CREEPING CHARLIE -See Primrose 

CREEPING MINT, CREEPING THYME - See Salvia 

CREPIS — See Chrysanthemum 



196 CRESS 

CRESS -See Cabbage 

CRIMSON DAISY -See Chrysanthemum 

CRINUM-See Daffodil 

CROCANTHEMUM - See Sunrose 

CROCOSMIA, CROCUS -See Gladiolus 

CROSSVINE - See Bignonia 

CROTALARIA - See Pea 

CROTON (Codiaeum) 

1. Anthracnose, Lea] and Stem Spot — Widespread. Yellowish-gray leaf spots which 
later turn whitish and dry out. Control: Keep water off the foliage. Apply zineb 
or captan sprays before wet periods. 

2. Root Rot — See (34) Root Rot under General Diseases. May be associated with 
nematodes (e.g., reniform) . 

CROWFOOT -See Delphinium 

CROWNBEARD - See Chrysanthemum 

CROWN IMPERIAL -See Tulip 

CROWN - OF - THORNS - See Poinsettia 

CROWNVETCH - See Pea 

CRYOPHYTUM - See Iceplant 

CRYPTOGRAMMA - See Ferns 

CRYPTOMERIA - See Juniper 

CUCUMBER [COMMON and ENGLISH FORCING], 

MUSKMELON, CANTALOUP, HONEYDEW MELON, CASSABA, 

WINTER MELON, WEST INDIAN GHERKIN (Cucumis); 

CHINESE WAXGOURD (Benincasa); BRYONOPSIS; WATERMELON, 

CITRON (Citrullus); SQUASH [SUMMER or BUSH, WINTER], 

PUMPKIN [WINTER CROOKNECK or CUSHAW, COMMON], 

VEGETABLE-MARROW (Cucurbita); GOURDS, CALABASH, 

VEGETABLE SPONGE, GUINEA BEAN, NEW GUINEA BEAN (Cucurbita, 

Lagenaria, Luffa, and Trichosartthes); MOCK - CUCUMBER (Echinocystis); 

MELOTHRIA; BALSAM-APPLE, BALSAM-PEAR (A4omordica; ; 

CHAYOTE (Sechium); CURUBA, CASSABANA (Sicana) 

I. Anthracnose (squashes and pumpkins almost immune) —General in warm, hu- 
mid areas. Often destructive. Round to angular, reddish-brown to almost black 
spots on leaves. Spots may later dry and tear out with leaves withering. Light 
brown to black, elongated streaks on stems and petioles. Young fruit may blacken, 
shrivel, and drop off. Older fruits have small to large, round, sunken spots which 
are water-soaked at first and later dark green to black, with flesh-colored, oozing 
centers. Bacterial Soft Rot often follows. Control: Plant western-grown, disease- 
free seed or soak seed for 5 minutes in a warm (60° to 80° F.) , 1:1,000 solution of 
mercuric chloride. See pages 85 or 427 for precautions. Wash seed 5 minutes in 



CUCUMBER 197 



running water, dry, and dust with captan, thiram, chloranil, or Semesan plus di- 
eldrin or lindane. See Table 13 in the Appendix. Cucumber seed can be soaked 
in hot water (122° F.) for 20 minutes as a substitute. Dry and dust as for the 
mercuric chloride treatment. Plow under or burn crop debris after harvest. Keep 
down weeds. Three-year rotation. Plant in well-drained soil. Apply captan, zineb, 
thiram, or maneb at 7- to 14-day intervals, starting about when vines "start to 
run." Use ziram or captan on young plants. Normally resistant watermelon vari- 
eties: Blackstone, Black Kleckley, Charleston Gray, Congo, Dunbarton, Early Re- 
sistant Queen, Fairfax, Garrisonian, Hope Diamond, and Spaulding. Tolerant 
cucumber varieties: Ashe, Ashley, Fletcher, Palmetto, Santee, and Stono. 

2. Scab, Spot Rot, Pox — Primarily a disease of cucumber, muskmelon, summer squash, 
pumpkin, watermelon, and gherkin. General in moist areas. Small, angular, water- 
soaked or pale green spots on the leaves which later turn white to gray. Spots tear 
away leaving ragged holes. Similar elongated spots occur on the petioles and 
stems. Small, gray, slightly sunken, oozing, gummy spots on fruit increase in size 
and become sunken, dark cavities lined with a dark olive-green mold. Fruit are 
often later destroyed by Bacterial Soft Rot. See Figure 28D under General Dis- 
eases. Control: Same as for Anthracnose (above) , except for resistant varieties. 
Resistant cucumbers: Ashe, Dark Green Slicer, Fletcher, Highmoor, Hybrid Long 
Green, Hycrop Hybrid Pickling, Improved Highmoor, Maine No. 2, Nappa 63, 
Wisconsin SMR-9, SMR-12, SMR-15, and SMR-18. 

3. Leaf Spots, Leaf Blights (often serious on muskmelon) — General. Small, round 
to irregular, water-soaked, yellow, tan, gray, brown, or black spots on leaves. 
Spots may enlarge, turn dark brown, and become zoned (target spots) . See Figure 
102. Center leaves may wither and fall early. Fruit may sunburn and ripen pre- 
maturely. Most serious in warm, moist weather. Spots may also occur on the 
petioles, stems, and fruit. Control: Same as for Anthracnose (above) . Keep plants 
growing vigorously by fertilizing and watering. Normally resistant muskmelon va- 
rieties: Edisto, Hales Best 936, and Purdue 44. 

4. Angular Leaf Spot, Bacterial Spot (primarily cucumber, muskmelon, gourds, 
squash, West Indian gherkin, and bryonopsis) — General. Small, angular, water- 
soaked spots on the leaves which later dry, turn gray, and drop out. Leaves ragged. 
Similar spots may occur on the stems and petioles. Round, water-soaked spots on 
the fruit. Fruit drop often follows. A whitish crust may develop on the surface 
of leaf, stem, and fruit spots. Disease is favored by frequent summer rains. Con- 
trol: Treat seed as for Anthracnose (above) . Two-year rotation. Apply a mixture 
of zineb or maneb (1 tablespoon) and fixed copper (li/g tablespoons per gallon) , 
at 5- to 7-day intervals, during warm (75° F.) , wet weather, starting when plants 
start to vine. Streptomycin sprays in the field are also effective. Destroy plant 
debris after harvest. Do not work among wet plants. Control insects with methoxy- 
chlor or dieldrin and malathion. Watermelon, muskmelon, and squash varieties 
differ in resistance. Santee cucumber has fair resistance. If Anthracnose or Scab 
is present, alternate copper with maneb or captan. 

5. Bacterial Wilt (primarily cucumber, muskmelon, squash, gherkin, pumpkin, and 
gourds) — General and serious. Vines rapidly wilt, wither, and die starting with 
one or a few leaves on one vine. Juice from cut stems may be milky or sticky and 
stringy. Squash vines are dwarfed. See Figure 3 IB under General Diseases. Water- 
melon is almost immune. Control: Rotate. Control cucumber beetles and other in- 
sects which transmit the causal bacteria. Use dieldrin or methoxychlor at 5- to 7- 
day intervals before blooming and malathion at 5-day intervals after blooming. 
Start as plants crack soil. For a few plants in the garden, protect by starting under 



198 CUCUMBER 




Fig. 102. Watermelon leaf spot. 



Fig. 103. Powdery mildew of squash. 
(Iowa State University photo) 



Hotkaps and then enclosing in cheesecloth tents to keep out insects. Pull up and 
destroy wilted plants. Resistant cucumber varieties: certain pickling strains. Fairly 
resistant squash: Boston Marrow, Buttercup, Butternut, Delicious, Early Market, 
Mammoth Chili, Table Queen or Acorn, and Warren. 

Fusarium Wilt, Fruit Rots (primarily watermelon, citron, muskmelon, cucumber, 
and mock-cucumber) — General in warm areas. Plants stunted and often yellow. 
Leaves suddenly wilt, wither, and runners gradually die. Yellow to dark brown 
streaks inside stems when cut. Cantaloup fruit show sunken, irregular spots. Seeds 
may rot in the soil. Seedlings often wilt and collapse. Roots gradually decay. See 
Figure 29C under General Diseases. Control: Treat seed as for Anthracnose 
(above) . Sanitation. Resistant watermelons, where adapted: Baby Kleckley, Black- 
lee, Blue Ribbon, Bush Desert King, Calhoun, Charleston Gray, Charleston Gray 
133, Congo, Crisscross (Chris cross), Dixie Hybrid, Dixie Queen W.R., Early Re- 
sistant Queen, Fairfax, Georgia W-R, Harper Hybrid, Hawklee, Hope Diamond, 
Iowa King, Improved Kleckley Sweet No. 6, Improved Stone Mountain No. 5 and 
19, Klondike R-7, Klondike RS-57, Leesburg, Queen Hybrid, Shipper, Spaulding, 
Summit, and White Hope. Resistant muskmelons: Delicious 51, Early Market 
Hybrid, Golden Honey, Harper Market, Harvest Queen, Honey Rock, Iroquois, 
Minnesota Midget, Minnesota Honey, Queen of Colorado, Spartan Rock, and 



CUCUMBER 199 



Supermarket Hybrid. The Persian Honeydew, Honeyball, and Cassaba melons 
are also relatively resistant. Control nematodes. See Root-knot (below) . Keep 
plants growing vigorously by fertilizing and watering. 

7. Mosaics — General and serious. Yellow-green and dark green mottling or distor- 
tion of leaves. Leaves often stunted and curled. Vines stunted, may be yellowed and 
"bunchy." Fruits often show yellow, yellow-green, or pale green spotting and 
mottling. May be warty or knobby with a bitter taste. Squash fruit may also show 
rings. If severe, all leaves except those at runner tips (rosettes) may die. Yield 
is reduced. Control: Rigidly control weeds (e.g., bur and wild cucumber, catnip, 
horsenettle, milkweed, motherwort, pokeweed, white cockle, wild groundcherry, 
and many others) . Destroy first infected plants after first applying malathion. Con- 
trol aphids and cucumber beetles which transmit the viruses. Use malathion and 
methoxychlor at 5-day intervals. Plant virus-free muskmelon and squash seed. Resist- 
ant cucumber varieties: Burpee Hybrid, Challenger, Challenger Hybrid, Early Sure- 
crop Hybrid, Hybrid Long Green, Hycrop Hybrid Pickling, Jet, Nappa 61, Ohio 
MR-17, MR-25, MR-200, Puerto Rico 10 and 27, Resistant Burpee Hybrid, Sensa- 
tion Hybrid, Surecrop, Tablegreen, Total Marketeer, Vaughan's Hybrid, Wisconsin 
SMR-9, SMR-12, SMR-15, and SMR-18. Resistant muskmelons may be available 
soon. Zucchini squash has tolerance. 

8. Powdery Mildew — General. May be destructive. White or brownish mealy growth 
mostly on the upper side of leaves and young stems. See Figure 103. Occasionally 
on muskmelon and watermelon fruit. Leaves and young stems may wither and 
die. Plants are weakened or stunted. Fruit may sunscald or ripen prematurely. 
Control: Keep down weeds. Apply Karathane or fixed copper, one to three times, 
7 to 10 days apart, depending on the severity. Start when mildew is first seen. 
Resistant muskmelons: Desert Sun, Edisto, Georgia 47, Gold Cup, Golden Gate 45, 
Hale's Best Powdery Mildew Resistant 45, Homegarden, Honey Ball 306, Powdery 
Mildew Resistant 6, 45, and 88, and Seminole. Tolerant cucumber varieties: Ashe, 
Ashley, Fletcher, Palmetto, Stono, Yates Conqueror, and Yates Invader. 

9. Downy Mildews — General in warm, moist areas. Irregular to angular, yellow to 
brownish areas on the upper side of leaves near the center of the hill. Underside 
of diseased leaves may show a pale, grayish-purple mold following damp weather. 
The mold may vary from white to nearly black in color. Spots enlarge rapidly 
causing the leaves to wither and die. May resemble frost injury as entire vines 
are killed. Fruit are often nubbins with poor flavor. See Figure 20C under Gen- 
eral Diseases. Control: Apply maneb, zineb, or fixed copper at weekly intervals 
in wet weather, starting when vines "begin to run." Resistant cucumbers: Ashe, 
Ashley, Barclay, Burpee Hybrid, Challenger, Dark Green Slicer, Fletcher, P-51 
DMR, Palmetto, Palomar, Santee, Sensation Hybrid, Supermarket Hybrid, Stono, 
Surecrop Hybrid, and Total Marketeer. Challenger Hybrid has tolerance. Re- 
sistant muskmelons: Early Market Hybrid, Edisto, Georgia 47, Golden Model, 
Granite State, Homegarden, Rio Gold, Rio Sweet, Seminole, Smith's Perfect, 
Supermarket Hybrid, and Weslaco F and H. Watermelon varieties also differ in 
resistance. Control cucumber beetles with malathion, methoxychlor, or dieldrin. 
See under Bacterial Wilt (above) . 

10. Curly-top — Western states. Vines stunted. Young tip leaves bend upward, are often 
a darker green than normal and dwarfed while older leaves turn yellow. Leaves 
puckered and cupped downward. Fruit dwarfed with poor flavor. Yield is re- 
duced. Control: Keep down weeds. Destroy infected plants. Control leafhoppers 
which transmit the virus. Use dieldrin or malathion as given under Bacterial Wilt 
(above) . Resistant pumpkins: Big Tom, Calhoun, Chirimen, Cushaw, Kentucky 



200 CUCUMBER 

Field, Sweet Cheese, and Tennessee Sweet Potato. Resistant squashes: Long White 
Bush, and Marblehead (Umatillo and Yakima strains) . Resistant vegetable-mar- 
rows: Boston Creek, Bush Green, Green of Milan, Long Bush Green, Long White 
Bush, and Zuchetta Nostrana Nana. 

11. Ringspot — May closely resemble mosaic. Irregular, black, dead areas on water- 
melons. Leaves may show small brown dots surrounded by light yellow borders. 
Concentric rings often formed on fruit. Fruit rots may follow. See (17) Spotted 
Wilt under General Diseases. 

12. Aster Yellows — Plants stunted and yellowed. Numerous secondary shoots and 
green, aborted flowers may develop on squash and vegetable-marrow. Control: 
Keep down weeds. By using dieldrin before bloom and malathion after, control 
leafhoppers which transmit the virus. See under Bacterial Wilt (above) . Destroy 
infected plants when disease is first seen. 

13. White Wilt, Cottony Rot, Southern Blight, Stem Rot, Watery Soft Rot - Stem rots 
and dries up at the soil line. A cottony mold grows on the rotted area. Leaves turn 
yellow and wilt. Infected fruits are soft and watery. May be covered with a cot- 
tony mold. Control: See under Bean. 

14. Fruit Spots and Rots, Storage Rots — Cosmopolitan. See under Carrot. Rot often 
starts where fruit rest on damp soil. Rotted area may be covered with white, 
black, green, blue, or pink mold growth. Control: Plant in well-drained soil. 
Cucumber and watermelon varieties differ in resistance. Spray in the field as for 
Anthracnose (above) . Store mature, dry, sound, blemish-free squash and pumpkin 
fruit at 50° to 60° F. with low relative humidity (80 per cent) after curing at 
75° to 85° F. Check with your extension horticulturist. Handle fruit with care. 
Do not pile fruit over three deep in storage. Where practical in the garden, rest 
fruit on a dry surface (e.g., a dry mulch) . Four-year rotation. 

15. Gummy Stem Blight, Stem End Rot, Leaf Spot (primarily cucumber, muskmelon, 
pumpkin, squash, and watermelon) — Widespread. Small to large, water-soaked, 
gray fruit spots which turn black and gummy. Leaf spots are gray to brown. Leaves 
may turn yellow and wither. Stem spots oily green in color and gummy. Vines 
may wilt and die back. Control: Same as for Anthracnose (above) . Varieties differ 
in resistance. 

16. Seed Rots, Damping-off — General. Seeds rot. Stand is poor. Seedlings wilt and col- 
lapse. Control: Treat seed as for Anthracnose (above) . Apply a seedbed spray of 
captan or ziram (l]/ 2 tablespoons per gallon. Use 1 gallon per 125 square feet.) 
every 5 to 7 days when soil temperature is below 75° F. 

17. Root Rots — See under Bean, and (34) Root Rot under General Diseases. May be 
associated with nematodes (e.g., burrowing, dagger, naccobus, pin, ring, reniform, 
root-knot, root-lesion, spiral, stem, sting, stubby-root, stunt or stylet) . Control: 
Same as for Anthracnose (above) . Plant in disease-free soil. 

18. Root-knot — General in southern states. Plants unthrifty and stunted. May wilt on 
hot days. Swellings or small galls on the roots. Yield is reduced. See Figure 50B 
under General Diseases. Control: Rotate. If necessary, fumigate the soil in the fall 
after harvest using D-D or Telone. Follow the manufacturer's directions. Many 
varieties of cucumber are highly resistant. Resistant squashes: Black Zucchini, 
Butternut, Caserta, and Early Prolific Straight Neck. The resistance or susceptibility 
of varieties often depends on what Root-knot species or subspecies are present. 
Most cantaloups are very susceptible. 

19. Verticillium Wilt — Plants suddenly wilt, wither, and shrivel up. Brown to black 
streaks inside the stem. See (15B) Verticillium Wilt under General Diseases. Melon 
varieties differ in susceptibility. 



CURRANT 201 

20. Blossom Blight — Blossoms are blighted. May be covered with a dense mold. Young 
fruit rot and drop off. Rot usually starts at the blossom end. Control: Spraying as 
for Anthracnose and Downy Mildew (both above) is probably beneficial. Plant 
in well-drained soil. Rotate. Remove and destroy rotting flowers and fruits when 
first noticed. 

21. Bacterial Spot (primarily cucumber, gourds, pumpkin, and squash) —Small, round 
to angular leaf spots between the veins with bright yellow borders. Spots may run 
together blighting the whole leaf. Spots do not drop out. Control: Same as for 
Angular Leaf Spot (above) . 

22. Sooty Mold — Black mold on foliage and fruit following attack by insects. Control: 
Spray to control insects. See under Bacterial Wilt (above) . 

23. Crown Gall — See (30) Crown Gall under General Diseases. 

24. Web Blight — Southeastern states. See under Bean. 

25. Stem Streak, Dieback — Small pink to tan spots on the stems and petioles which 
soon run together forming long streaks. Affected parts are girdled causing killing 
and collapsing of the leaves and the portion of the vine beyond. Stems later appear 
brown. Control: Keep plants growing vigorously by applying adequate amounts of 
a balanced fertilizer based on a soil test. Otherwise same as for Anthracnose 
(above) . No resistant varieties are available. 

26. Boron Deficiency (primarily squash) — Leaves stunted, yellowed, cupped down- 
ward, and brittle. Petioles are curled and thickened. Control: Have the soil tested 
and apply borax as recommended. 

27. 2,4-D Injury — See under Grape. Melons are very susceptible. 

28. Blossom-end Rot (primarily squash and watermelon) — See under Tomato. 

29. Chlorosis — Deficiency of iron, manganese or zinc. See page 17. 

CUCUMBER - TREE - See Magnolia 

CULVERSROOT-See Speedwell 

CUNILA-See Salvia 

CUPHEA — See Cigarflower 

CUP - PLANT — See Chrysanthemum 

CUPRESSUS - See Juniper 

CURRANT [ALPINE or MOUNTAIN, CLOVE (BUFFALO or MISSOURI), COMMON 

or GARDEN RED, EUROPEAN BLACK, FLOWERING, GOLDEN, NORTHERN RED, 

RED-FLOWERED or WINTER, SIBERIAN, WAX], WINTERBERRY, 

GOOSEBERRY [EUROPEAN, FUCHSIA-FLOWERED, HAIRYSTEM ] (Ribes) 

1. Leaf Spots, Anthracnose, Spot Anthracnose or Scab — General. Small, dark spots on 
the older leaves which may develop gray centers. Spots may run together forming 
large brown blotches. The lower leaves are affected first. Leaves often turn yellow 
and drop early. Fruit may be spotted and reduced in size and number. Dark, 
sunken spots may also occur on the young canes and leaf stems. See Figure 104. 
Control: Space plants. Prune to open up centers of plants. Where practical, collect 
and burn fallen leaves. Apply fixed copper, zineb, maneb, phaltan, or ferbam fol- 
lowing the spray schedule in the Appendix (Table 10) . Currant and gooseberry 
varieties differ in resistance to Anthracnose. Welcome gooseberry is resistant. 



202 



CURRANT 





Fig. 105. Bacterial soft rot of cyclamen. 



Fig. 104. Currant leaf spot and anthrac- 
nose. 



2. Powdery Mildews — General. Most common and serious on gooseberry. Leaves, 
young shoots and berries are covered with powdery, bluish-white, or light grayish 
mold patches which later turn a rusty-brown color. Leaves and shoot tips may be 
stunted and distorted. Leaves attacked by mildew drop early. Berries may be 
dwarfed and cracked. Control: Apply Karathane plus spreader-sticker as the buds 
start to swell, just before, and just after bloom. Avoid shade and crowding of 
plants. Prune to "open up" plants. Currant and gooseberry varieties differ in resist- 
ance. 

3. Fruit Rots — General. Fruit rots near picking time. Mold growth may form over 
rot spots. May be serious in cool, humid weather. Control: Same as for Leaf Spots 
(above) . Space plants — keep pruned. If preharvest period is wet, apply captan at 
5-day intervals. 

4. Rusts (primarily Blister and Cluster cup) — Widespread. Small, yellowish to brown, 
dusty pustules on undersurface of leaves. Bright orange to reddish-yellow or red- 
dish-brown pustules appear on upper surface. Leaves may be curled, thickened, and 
drop early. Most common on the older leaves. Control: Do not plant susceptible 
currants and gooseberries (Ribes) within 1,000 feet of 5-needle pines. These plants 
are alternate hosts of White Pine Blister Rust; see under Pine. Quarantine regu- 
lations prevent the planting of susceptible currants and gooseberries in areas where 
white pine is an important lumber tree. Check with your state department of agri- 
culture before planting currants and gooseberries. Destroy nearby sedges (Carex 
spp.) , alternate hosts of Cluster Cup Rust. Destroy rust-susceptible wild Ribes. 
Apply sprays as for Leaf Spots (above) . Several weekly applications of ferbam 
are effective between bud burst and flowering. Be sure to cover both leaf surfaces. 

5. Dieback, Twig Cankers, Black Pustule, Cane-knot Canker, Cane Blights — Wide- 
spread. Tip leaves on young canes suddenly wilt and die. Canes are blighted, dry 
up, and die back. Most conspicuous just before the fruit ripens. A gray mold, or 



CYCLAMEN 203 



small, coral-pink to black pimples may be evident on blighted parts. May follow 
winter injury. Control: Cut out and burn blighted canes before leaves appear. Take 
cuttings from disease-free plants. Plant in well-drained soil. Avoid heavy applica- 
tions of fertilizer high in nitrogen. Spray as for Leaf Spots (above) . 

6. Collar Rot — Widespread. Perennial hooflike or shelflike structures, mostly at or 
near the ground line on older bushes. See (23) Wood Rot under General Diseases. 
Plants die slowly over several years. 

7. Root Rots — See under Apple, and (34) Root Rot under General Diseases. 

8. Mosaic (primarily red currant) — Round, light green to yellowish spots on the 
leaves. Spots enlarge and run together forming irregular bands along the leaf veins. 
Leaves may become yellowish with scorched margins. Plants gradually decline in 
vigor, become stunted, produce less and less fruit. Control: Dig up and destroy in- 
fected plants when first seen. Control insects with malathion sprays. Plant virus- 
free stock from a reputable nursery. Destroy nearby wild currants and gooseberries. 

9. Gooseberry Sunscald — Fruit is soft, pale, and drops early. Often it is covered by 
various types of mold growth. Control: Spray as for Leaf Spots (above) . Keep 
plants growing vigorously (fertilize, and water during dry periods) . 

10. Downy Mildew (gooseberry) —See (6) Downy Mildew under General Diseases. 

11. V erticillium Wilt — Uncommon. See under Barberry, and (15B) Verticillium Wilt 
under General Diseases. 

12. Chlorosis — See under Maple. 

13. Thread Blight — Southeastern states. See under Walnut. Control: Spray as for Leaf 
Spots (above) . 

14. Bud Nematode — California. See (20) Leaf Nematode under General Diseases. 
Control: Dip infested cuttings in hot water (110° F.) for 30 minutes. 

CURUBA, CUSHAW-See Cucumber 

CUSHION - PINK - See Carnation 

CYCLAMEN 

1. Gray-mold Blight, Botrytis Bud and Leaf Rot, Petal Spot — Cosmopolitan and 
serious. Buds may be rotted. Leaves, stalks, and flower petals are spotted. A dense 
gray mold may cover affected areas in damp weather. Rot may spread gradually 
into the corm, killing the plant. Control: Avoid overcrowding and high rates of 
nitrogen fertilizer. Increase air circulation. Pick off and destroy affected plant 
parts. Spray plants and drench soil using captan, maneb, or zineb. 

2. Stunt — Plants and leaves stunted but not killed. Leaves may turn yellow. Flowers 
characteristically open below the leaves. Reddish-brown dead areas appear when 
corms are cut through. Control: Destroy infected plants as they will not recover. 
Plant disease-free corms or start seed from healthy plants in clean or sterilized 
soil. See "Soil Treatment Methods and Materials" in the Appendix. 

3. Bacterial Soft Rot, Tuber Rot — Leaf and flower stems wilt and droop. Soft, slimy, 
foul-smelling rot of the petioles and corm (or tuber) . See Figure 105. Control: 
Avoid overshading, overstimulating with fertilizer, overwatering, and wounding 
of underground parts. Plant in sterilized soil. Destroy affected parts. Keep water 
off the foliage. 

4. Root-knot — Cosmopolitan. Cyclamen is highly susceptible. See (37) Root-knot 
under General Diseases. 



204 CYDONIA 

5. Root Rot — Plants sickly. Easily pulled up. Roots and corms are black or white 
and rotted. May be associated with nematodes (e.g., root-knot, root-lesion) . See (34) 
Root Rot under General Diseases. Control: Same as for Bacterial Soft Rot (above) . 
Some control, if early enough, by immersing root clump in a thiram or captan solu- 
tion. 

6. Leaf Spots, Leaf and Bud Blight, White Mold — Various types of dead spots in 
leaves. Leaves may wither and fall early. Buds may be blighted. Control: Pick off 
and destroy infected leaves as they appear. Increase air circulation. Keep water off 
the foliage. Spray or dip potted plants at 10- to 14-day intervals using captan or 
zineb. Plant disease-free seed in new or sterilized soil. 

7. Seedling Blight, Damping-off — Seedlings wilt and collapse from a rot at the soil 
line. Usually starts in a few plants and spreads outward. Control: Plant in sterilized 
soil. Avoid overwatering and poorly drained soil. Keep the humidity down. If 
disease starts, sprinkle affected areas with captan or zineb solution (1 tablespoon 
per gallon) . Repeat 5 to 7 days later. 

8. Leaf Nematode — See (20) Leaf Nematode under General Diseases. 

9. Fusarium Wilt — See (15A) Fusarium Wilt under General Diseases. Control: Same 
as for Stunt (above) . 

CYDONIA -See Apple 

CYMBIDIUM - See Orchids 

CYNARA-See Lettuce 

CYNODON — See Lawngrass 

CYNOGLOSSUM - See Mertensia 

CYPRESS - See Umbrellaplant 

CYPHOMANDRA - See Tomato 

CYPRESS, CYPRESSUS - See Juniper 

CYPRESSVINE - See Morning - glory 

CYPRIPEDIUM-See Orchids 

CYRILLA - See Buckwheat - tree 

CYRTOMIUM, CYSTOPTERIS - See Ferns 

CYTISUS-See Broom 

DAFFODIL, JONQUIL, NARCISSUS [MINIATURE, POETAZ or CLUSTER 

FLOWERED, POET'S POLYANTHUS, and TRUMPET] (Narcissus); AMARYLLIS 

[HYBRID, MAGIC LILY 1, BELLADONNA-LILY (Amaryll's); RAINLILY 

(Cooperia); CRINUM; AMAZON - LILY (Eucharis); SNOWDROP (Galanthus); 

SPIDERLILY (Hymenocallis); SNOWFLAKE (Leucojum); HARDY AMARYLLIS 

ttycons); TUBEROSE (Polianthes); GUERNSEY-LILY (Nerine); WINTER- or 

FALL-DAFFODIL (Sternbergia); SCARBOROUGH-LILY (Vallota); ATAMASCO- 

LILY, ZEPHYRLILY (Zephyranthes) 

I. Bulb Rots, Root Rots — General. Plants fail to emerge, or only sickly, stunted 
shoots come up with weak yellowish or blighted leaves. Bulbs rot usually starting 
at base. Rot spreads through bulbs to neck. Roots are often rotted. Blue, green, 
black, gray, or white mold growth often evident on bulb or between the bulb 



DAFFODIL 205 

scales. Usually associated with bulb mites and nematodes (e.g., lance, root-lesion 
or meadow, spiral) . See Figure 49A under General Diseases. Control: Plant only 
high quality, well cured, disease-free bulbs free of cuts, bruises, or other injuries. 
Discard infected bulbs. Four-year rotation. Space plants. Avoid wounding bulbs 
and overfertilization, especially with nitrogen. Remove winter foliage mulch in 
early spring. Carefully remove and burn infected plants including all underground 
parts together with several inches of surrounding soil. Treat narcissus and snow- 
drop bulbs by soaking in a solution containing Ceresan 2 per cent, Emmi, Puratized, 
Mersolite 8, Dowcide B, or captan following the manufacturer's directions. Or 
soak bulbs in hot water-formalin solution as for Stem and Bulb Nematode (below) . 
Dry bulbs rapidly after treatment and plant immediately in well-drained soil which 
is clean or sterilized (pages 437-44) . Narcissus varieties differ in resistance. Certain 
rots (Sclerotium and Black Rot) of narcissus are controlled by Terraclor (PCNB) 
dust or spray applied in the furrow at planting time, following the manufacturer's 
directions. Soak amaryllis bulbs before planting for 2 hours in a 1:1,000 solution 
of mercuric chloride. Plant 1 to 2 days after treatment. 

2. Mosaics, Yellow Stripe, Flower Streak, Gray Disease — General. Light green, gray- 
ish-green, dark green, or bright yellow streaks or an indefinite mottling of the 
leaves. Flowers often stunted, distorted, and mottled or yellow-streaked. Flower 
production decreases. Plants more stunted each year. Leaves may be spirally twisted 
and roughened. See Figure 32D under General Diseases. Control: Destroy infected 
plants when first found, in bloom, and again late in the season. Keep down weeds. 
Control aphids using malathion or lindane. Avoid growing near onions. Plant only 
the largest virus-free bulbs available. 

3. Narcissus White Streak, Paper Tip — General. White streaks develop in leaves after 
bloom. Tips then dry up and become papery. Finally wilt and collapse. Bulbs are 
small. Plants mature (decline) very rapidly. Control: Same as for Mosaics and 
Yellow Stripe (above) except destroy diseased plants after blooming. Replant using 
only the largest bulbs. 

4. Fire, Botrytis Blight, Gray-mold or Leaf Blight, Flower Spot — Widespread. Often 
follows chilling. Watery, light brown spots on the flowers. Later, bright yellow, 
elongated spots with chocolate-brown or reddish-brown centers develop on the 
leaves. Diseased areas rot rapidly in warm, damp weather. Narcissus varieties differ 
in resistance. Control: Same as for Bulb Rots (above) . Keep down weeds. Collect 
and burn tops in the fall. If practical, carefully pick off and burn affected parts as 
they occur. Apply zineb, maneb, ferbam, captan, dichlone, or fixed copper plus 
spreader-sticker several times, at about weekly intervals, starting when the leaves 
are 4 to 8 inches tall. Spray just before wet periods when infections occur. 

5. Leaf Scorch, Red Spot or Blotch, Red Fire Disease — General. Small, red to reddish- 
brown or purplish spots or streaks, often with a yellow border, develop on the 
leaves and flower stalks. Spots may enlarge and run together causing large blotches. 
Leaves and flower stalks may wither and die prematurely. Flowers may be spotted 
dark red or brown. See Figure 106A. Control: Same as for Fire and Bulb Rots (both 
above) . Indoors, keep water off the foliage. Avoid overwatering, high humidity, 
high temperatures, and wounding plants. Increase light. 

6. Bud and Leaf Nematode, Stem and Bulb Nematode, Browning or "Ring" Disease 

(narcissus, lycoris) — In all commercial bulb-growing areas. Leaves stunted, thick- 
ened, and twisted with small, yellowish blisters. Bulbs when cut across show yellow 
to dark brown rings of infested scales. Badly infested bulbs fail to sprout. See 
Figure 107, and (38) Bulb Nematode under General Diseases. Control: Dig up and 
burn infested bulbs and adjacent ones which appear healthy, plus 6 inches of 
surrounding soil. Three-year rotation with nonbulb plants. Keep down weeds. 



206 



DAFFODIL 



ft 





106. A. Leaf scorch of narcissus, 
White mold of narcissus. 



Fig. 107. Stem and bulb nematode dam- 
age to narcissus. 



Plant only large, disease-free bulbs in light, well-drained soil fumigated with D-D 
or EDB, where practical. Commercial growers treat properly cured, dormant 
narcissus bulbs by presoaking in water at room temperature (75° F.) for 2 hours 
followed by soaking 3 to 4 hours in a solution of hot water at exactly 110° to 111° F. 
and formalin in a proportion of 1:200 or 1 pint of formalin in 25 gallons of water. 
This treatment also controls mites, bulb flies, and fungi. 
7. Narcissus ''Smoulder/' Neck Rot (narcissus, snowdrop) — Plants stunted or missing. 
Shoots may be brown and blighted with crumpled leaf tips. Flower stems may rot 
and flowers develop brown spots. Yellowish-brown rot of bulb in storage. Small, 




Fig. 108. Narcissus "smoulder. 



DAPHNE 207 



flattened, black bodies (sclerotia) develop on the "nose" of the bulb, between 
the husks, or at both places. See Figure 108. Serious in cold, wet weather. Control: 
Same as for Bulb Rots (above) . Destroy badly infected plants or plant parts. Spray 
as for Fire (above) . Keep down weeds. 

8. Narcissus White Mold, Ramularia Blight — Pacific Northwest. Sunken, yellow to 
gray spots or streaks appear on the leaves, then enlarge and turn dark green to 
yellowish-brown with a yellow margin. Leaves and flower stalks rot quickly. Affected 
areas are covered with a white, powdery mold in wet weather. May resemble frost 
injury. See Figure 106B. Varieties differ in susceptibility. Control: Same as for Fire 
(above) . Spray with fixed copper or zineb plus spreader-sticker. 

9. Amaryllis Spotted Wilt — Numerous pale yellow or white spots on the leaves. Red- 
dish-brown spots or red lines may develop, especially along the leaf edges. Leaves 
usually later turn yellow and die. Control: Same as for Yellow Stripe (above) . Con- 
trol thrips which transmit the virus. Use DDT and malathion. 

10. Root-lesion (Meadow) and other Root-feeding Nematodes (e.g., lance, pin, sheath, 
spiral) — Plants and bulbs often stunted. Foliage turns yellow and withers pre- 
maturely in certain areas. Eventually the whole plant may wilt and die. Roots are 
few, short, and stubby. Often show dark spots or rot. Control: Plant in clean or 
sterilized soil (pages 437-44) . Use D-D, chloropicrin, or EDB following the manu- 
facturer's directions. 

11. Root-knot — See (37) Root-knot under General Diseases. Control: Same as for 
Root-lesion Nematodes (above) . Soak Tuberose tubers, offsets, or "seed" in hot 
water (120° F.) for 1 hour. 

12. Yellow Dwarf— Plants stunted and yellowish. See under Onion. 

IS. Leaf Spot — Small, water-soaked spots appear on the leaves after blooming is over. 
Spots enlarge, turn grayish-brown, and run together. Leaves often wither and die 
early. Control: Destroy spotted leaves. Spray as for Fire (above) . 

14. Rust (atamasco-lily, rainlily, zephyranthes) —Southern states. Yellow, orange, red- 
dish-brown, or black powdery pustules on leaves. Control: Spray as for Fire (above) . 
Destroy rusted leaves. 

DAHLIA — See Chrysanthemum 

DAHOON-See Holly 

DAISY — See Chrysanthemum 

DAMESROCKET - See Cabbage 

DANGLEBERRY - See Blueberry 

DAPHNE [CAUCASIAN, LILAC, WINTER], MEZEREUM, GARLAND FLOWER, 

SPURGE LAUREL (Daphne) 

1. Leaf Spots, Anthracnose — Widespread. Thick, brown, purplish, reddish, or irregu- 
lar greenish spots on the leaves. Leaves may later turn yellow, wither, and fall pre- 
maturely. Control: Pick off and burn infected leaves. Spray several times, 10 to 14 
days apart, using fixed copper, zineb, maneb, or captan. 

2. Twig Blight, Canker, Dieback — Twigs blighted. Twigs and branches die back. May 
be covered with small, coral-red "cushions." Control: Cut off and burn infected 
parts. Spraying as for Leaf Spots may be beneficial. 

3. Crown Rots, Stem Rot, Wilts — See under Delphinium. 

4. Mosaic — Leaves mottled yellowish-green. Plants may be stunted. Control: Destroy 



208 DASHEEN 

infected plants. Control insects which spread the viruses, using DDT and malathion. 
See (16) Mosaic under General Diseases. 

5. Winter Injury — Foliage scorched following an ice crust. 

6. Wilts (Verticillium and Fusarium) —Rare. See (15A) and (15B) Fusarium and 
Verticillium Wilts under General Diseases. 

DASHEEN -See Callct 

DATURA — See Tomato 

DAYFLOWER - See Tradescantia 

DAYLILY - See Hemerocallis 

DECUMARIA - See Hydrangea 

DEERGRASS, MEADOWBEAUTY (Rhexia) 

l.Leaf Spots — Spots of various colors, sizes, and shapes on leaves. Control: Pick off 
and burn spotted leaves. If serious enough, spray several times, 10 days apart, dur- 
ing rainy periods. Use zineb, maneb, or captan. 

DELPHINIUM, LARKSPUR [ BOUQUET, CANDLE or GARLAND, CHINESE, 

RED, ROCKET or ANNUAL, and SCARLET ] (Delph'm'um); MONKSHOOD, 

ACONITE (Aconitum); COLUMBINE (Aquileg'a); GOLDTHREAD (Coptis); 

CHRISTMAS-ROSE (Helleborus); PEONY, TREE PEONY (Paeonia); 

BUTTERCUP, CROWFOOT (Ranunculus); MEADOWRUE (Thalictrum) 

l.Stem Cankers, Southern Blight, Wilt, Stem, Crown, and Root Rots — General and 
serious. Stems stunted, suddenly or gradually wilt, may turn yellow, darken, and 
die. Often collapse. Infected plants are easily pulled up. Stems cankered or rotted 
at or near the soil line. May have a foul odor. Roots are often decayed. White 
fungus threads and tan to dark seedlike bodies (sclerotia) may form at the crowns. 
Control: Dig up and divide older clumps. Dig up and burn severely diseased plants, 
including 3 to 5 inches of surrounding soil. Plant disease-free stock or seed from 
disease-free plants. Treat suspicious delphinium seed by soaking in hot water (130° 
F.) for 10 minutes. Cool, dry, and plant. Plant in clean or sterilized soil (pages 
437-44) which is well-drained and in a sunny spot. Rotate. Avoid overwatering, 
wounding stems, and a wet mulch around crowns. In the fall after cutting and 
burning the tops, and again in early spring, drench crowns and surrounding soil 
several times, a week apart, using Semesan or a 1:2,000 solution of mercuric chlo- 
ride. See pages 85 or 427 for precautions. Certain rots are controlled by working 
Terraclor (PCNB) dust into the top 4 to 6 inches of soil, a week or more before 
planting. Or apply a soil drench of Terraclor 75 per cent (1 pint per square foot) . 
Follow the manufacturer's directions. Spraying in the spring as for Gray-mold 
Blights (below) is often beneficial. 

2. Gray-mold Blights, Botrytis Blight, Flower Blight, Bud Blast — General. Young 
shoots may wilt and collapse from a soft brown to black rot near the soil line. 
Buds turn brown or black and fail to open, or flowers are brown-spotted, watery, 
and matted. Large, irregular, brown blotches may occur on the leaves. A coarse 
gray mold grows on affected areas in damp weather. Peony buds that turn brown 
and dry from pea to marble size may be due to the feeding of thrips, frost in- 
jury (especially if the potash supply in the soil is low) , lack of water and soil 



DELPHINIUM 209 



nutrients, and other factors. See Figure 19B under General Diseases. Control: Cut 
and burn tops at ground level in the fall. Spray with captan, zineb, ferbam, or 
maneb (\i/ 2 tablespoons per gallon) plus spreader-sticker as the shoots emerge. 
Repeat 10, 20, and 30 days later. Apply the last spray as flowers start to open. 
Additional sprays at 2-week intervals after bloom may be needed if the period 
is rainy or humid. 

3. Mosaic, Ringspot — General. Symptoms variable. Plants may be stunted with 
mottled, pale green, and yellow leaves with lemon-yellow to orange-amber leaf 
spots, blotches, line patterns, bands, arcs, or striking, zoned rings with "green 
islands." Flowering may be prevented. See Figure 109. Control: Do not propagate 
from infected plants. Destroy diseased plants when first seen. Keep down weeds. 
Control insects, especially aphids, using malathion sprays. 

4. Delphinium and Aconitum Black Blotch, Bacterial Leaf Spot — Widespread in 
cool, wet weather. Small, water-soaked spots which later are irregular, shiny, and 
tarlike with yellow borders. Mostly on leaves, but also on buds, stems, and blos- 
soms. Lower leaves are infected first. See Figure 16C under General Diseases. 
Control: Plant disease-free stock in clean soil. Destroy infected leaves as they ap- 
pear. Cut and burn tops in the fall. If possible, keep water from splashing on 
the foliage. Three to 4-year rotation. Drench crowns and soil when plants are 6 
to 10 inches tall using zineb, maneb, fixed copper, or Semesan. Thereafter spray 
weekly with fixed copper and spray lime (3 tablespoons of each per gallon of 
water) , if serious enough. 

5. Powdery Mildews — General. Powdery, white mold growth on leaves. Varieties differ 
greatly in resistance. Control: Spray two or three times, 10 days apart, using Kara- 
thane, Acti-dione, or sulfur. Delphinium varieties differ in resistance. 

6. Yellows, Stunt, W itches' -broom , "Greens" — General. See under Chrysanthemum. 

7. Seed Rot, Damping-off — Cosmopolitan. Seed rot. Stand is poor. Seedlings wilt and 
collapse. Control: Sow seeds in sifted sphagnum moss or other suitable starting 
medium. 

8. Wilts (Fusarium and V erticillium) — Plants gradually wilt, wither, and die about 
blooming time, starting at the base. Insides of stems and crowns show green to 
brown or black streaks. Fusarium also causes light brown, water-soaked areas 
(cankers) on the stems. Control: Dig up and destroy infected plants. Plant disease- 
free stock in clean or sterilized soil that has not grown wilted plants. See "Soil Treat- 
ment Methods and Materials" in the Appendix. 

9. Crown Gall — See under Begonia, and (30) Crown Gall under General Diseases. 

10. Root-knot and Other Root-feeding Nematodes (e.g., dagger, lance, root-lesion or 
meadow, spiral, stem) — Small galls usually i/ 8 to 14 inch in diameter form on the 
finer roots (Root-knot) . Roots may die back or be stunted and bushy. Plants lack 
vigor, may be stunted, spindly, pale in color, and do not bloom normally. Con- 
trol: Plant nematode-free roots or planting stock in clean or sterilized soil (pages 
437-44). Drench around established plants using Nemagon, Fumazone, or VC-13 
Nemacide following the manufacturer's directions. Disinfest dormant peony roots by 
soaking in hot water (120° F.) for 30 minutes. 

11. Leaf Spots, Leaf Blight or Blotch, Anthracnose, Black Spot — Small to large leaf 
spots or blotches of various colors. May run together forming irregular dead areas. 
Leaves may wither and die prematurely. Similar spots may also occur on the stems, 
petioles, and flower petals. See Figure 110. Control: Cut and burn tops in the fall. 



210 



DELPHINIUM 





Fig. 110. Black spot of Christmas-rose. 



Fig. 109. Peony ringspot. 

Spray foliage as for Gray-mold Blights (above) . Propagate only from disease-free 
plants. 

12. Rusts (aconitum, buttercup, columbine, delphinium, meadowrue) —Widespread. 
Small yellow spots on the leaves. Alternate hosts include various grasses, barley, 
Prunus spp., and Polygonum viviparum. Control: Spray as for Gray-mold Blights 

(above) . 

13. LeMoine Disease of Peony — Common. Plants dwarfed with spindly shoots. Pro- 
duce no flowers. Roots irregularly swollen, short, and stubby. Control: Dig up and 
burn infected plants. Plant disease-free stock in a new location. 

14. Peony Crown Elongation Disease, Witches' -broom — Small leaves on dwarfed, slen- 
der shoots. Crowns elongated with weak buds at tips. Plants do not flower. Control: 
Same as for LeMoine Disease (above) . 

15. Leaf and Stem Smuts, White Smut — Blister-like swellings on leaves and leaf stalks 
which are later filled with a black powder. Control: Same as for Stem Rots (above) . 
Pick off and burn diseased parts before blisters open. 

16. Curly-top — Western states. Plants stunted with younger leaves curled and bunched 
on the main stem and side branches. See (19) Curly-top under General Diseases. 

17. Spotted Wilt, Ringspot (buttercup, columbine, dahlia, delphinium, peony) —See 
under Bellflower, and (17) Spotted Wilt under General Diseases. 

18. Leaf and Stem Nematode — See (20) Leaf Nematode under General Diseases. 
Branches may be aborted and foliage distorted. 

19. Flower Spot or Blight — Flower petals are spotted. Spots may enlarge, blighting 
the complete flower. See (31) Flower Blight under General Diseases. 

20. Peony Oedema, Measles — Many small, blister-like, brown or purple spots on the 
leaves and stems. Believed associated with high soil and air moisture. Control: 
Unnecessary. 

21. Peony Bud Blast — General. Buds reach the size of small peas but fail to develop 
further. Associated with low potassium in the soil, late spring frost or dry periods, 
root-knot infection, too deep planting in infertile soil, or excessive shade. Control: 
Avoid as many of these factors as possible. 

22. Downy Mildew (buttercup, meadowrue) — Occasional. See (6) Downy Mildew 
under General Diseases. Control: Spray as for Gray-mold Blights (above) . 

23. Chlorosis — See under Rose. May also be caused by low temperatures and wet soil. 



DOGWOOD 211 

24. Thread Blight — Southeastern states. See under Fig. 

25. Delphinium "Blacks" — Caused by minute cyclamen mites. Plants stunted, curled, 
and seriously deformed. Buds turn black. Are deformed and distorted. Dark brown 
to black streaks and blotches occur on the stems and petioles. Control: Check with 
your extension entomologist regarding a suitable spray program. 

26. Leaf Curl (peony) — Plants dwarfed with curled leaves. Flower stalks cracked. 
Control: Dig up and destroy infected plants. 

DENDROBIUM - See Orchids 

DENDROMECON - See Poppy 

DENNSTAEDTIA - See Ferns 

DENTARIA, DESERTPLUME - See Cabbage 

DESERT-WILLOW - See Cafalpa 

DEUTZIA-See Hydrangea 

DEVILSCLAW - See Proboscisflower 

DEVILWOOD-See Osmanthus 

DEWBERRY -See Raspberry 

DIANTHUS-See Carnation 

DICENTRA — See Bleedingheart 

DIDISCUS-See Celery 

DIEFFENBACHIA - See Calla 

DIGITALIS — See Snapdragon 

DILL — See Celery 

DIMORPHOTHECA - See Chrysanthemum 

DIOSCOREA - See Yam 

DIOSPYROS — See Persimmon 

DIPSACUS-See Teasel 

DIRCA — See Leatherwood 

DITTANY -See Salvia 

DODECATHEON - See Primrose 

DOGSTOOTH-VIOLET - See Erythronium 

DOGWOOD [BAILEY, BLOODTWIG, CHINESE, FLOWERING, GRAY, or 
PANICLED, JAPANESE CORNEL, PACIFIC, PAGODA or ALTERNATE-LEAVED, 
PINK, RED or TATARIAN, RED-OSIER, RED-TWIGGED, SIBERIAN, VARIEGATED, 
WHITE, WEEPING WHITE, YELLOW-TWIGGED], CORNEL [DWARF or 
BUNCHBERRY, ROUGHLEAF, SILKY]; OSIER [RED, WESTERN], CORNELIAN 
CHERRY, JAPANESE CORNELIAN CHERRY (Cornus); TASSELTREE, 
SILKTASSEL-BUSH (Garrya); TUPELO (SOUR GUM, BLACK GUM), WEEPING 

TUPELO (Nyssa) 

1. Dogwood Collar Rot, Trunk or Bleeding Canker — Widespread in eastern states. 

Trees lack vigor. Leaves dwarfed and pale green. Later the leaves turn yellow or 

prematurely red in late summer. Drop early. Twigs and branches are stunted. May 

die back; frequently on one side of the tree. Sunken canker on the lower trunk, 



212 



DOGWOOD 




Fig. 111. Dogwood collar rot. 



crown, or roots which enlarges slowly for several years. Girdles the trunk killing the 
parts beyond. See Figure 111. Cankers ooze sap in the spring. Trees may die. Con- 
trol: Dig up and burn trees showing large cankers (over halfway around) . Do not 
replant in the same soil for several years without drenching first with one part 
formalin in 50 parts of water or use zineb. Remove smaller cankers promptly. Cut 
out 1 I/O inches of surrounding "healthy" bark and discolored wood. See Figure 
10. Paint the wound edges with orange shellac. Swab the remainder with household 
bleach (diluted 1:5 with water), a 1:1,000 solution of mercuric chloride, or bor- 
deaux paste. Finally paint with tree wound dressing. Keep trees growing vigorously. 
Avoid wounding trunk during transplanting, mowing, etc. Keep the base of the 
trunk dry and free of wounds. Plant trees in well-drained soil. Control borers by 
painting or spraying the trunk and branches with DDT or dieldrin. Do not spray 
the foliage with DDT. Check with your county agent or extension entomologist re- 
garding timing of sprays. 



DOGWOOD 213 



2. Leaf Spots, Spot Anthracnose — Widespread. Spots of various sizes, shapes, and 
colors, often with dark purple to brown borders (Figure 112) . Spots on leaves may 
drop out leaving ragged holes. Common in wet seasons. Certain spots also occur on 
young stems, flowers, and berries. If severe, leaves may drop early. Flowers may be 
stunted and malformed. Control: Apply same spray materials as for Gray-mold 
Blight (below) or use maneb, phaltan, or phenyl mercury. Spray just before and 
after bloom. Then repeat monthly to August. Collect and burn fallen leaves in 
autumn. Keep trees pruned. 

3. Gray-mold Blight, Flower and Shoot Blight, Bud B Ugh t — Widespread in wet 
springs. Irregular brown areas on fading flowers and leaves. May be covered with 
a grayish mold in damp weather. Buds are blasted. Control: Apply captan or zineb 
just before, during, and after bloom. If possible, spray just before wet periods. 
Prune to keep trees open. 

4. Powdery Mildews — General. Leaves covered with white, powdery mold patches in 
late summer and fall. Control: If serious enough, add Karathane or sulfur to Leaf 
Spot sprays (above) . 

5. Twig Blights, Branch and Trunk Cankers, Dieback — Twigs and branches die back 
from girdling, discolored cankers. Control: Prune and burn infected branches back 
to healthy wood. Paint wounds promptly as for Collar Rot (above) . Keep trees 
vigorous by watering and fertilizing. Spraying as for Leaf Spots (above) should be 
beneficial. 

6. Root Rots — See under Apple, and (34) Root Rot under General Diseases. Often 
associated with root-feeding nematodes (e.g., dagger, lance, pin, root-knot, spiral, 
sting, stubby-root) . 

7. Wood Rots, Heart Rot — See under Birch, and (23) Wood Rot under General 
Diseases. 

8. Sooty Mold, Black Mildew — Mostly in southeastern states. See under Apple, and 

(12) Sooty Mold under General Diseases. 

9. Leaf Scorch — Margins of leaves turn light brown on trees growing in full sun and 
in poor soil. Scorch develops in July and August following hot, dry, windy weather. 
Control: Have the soil tested. Apply fertilizer as recommended. Prune trees to keep 
them growing vigorously. Water during summer dry periods. 

10. Sunscald — Results in death of young trees during the first few years following 
transplanting. Often due to sunscald, lack of soil moisture, and careless handling 
of trees too large for easy transplanting. Control: Transplant small trees into 
partial shade. Wrap or shade the south and southwest sides of the tree trunk. See 
under Apple, and Figure 12. Water and fertilize properly. 

11. Crown Gall — See under Apple, and (30) Crown Gall under General Diseases. 

12. Verticillium Wilt — See under Maple. 

13. Rust (dwarf cornel, tupelo) —Widespread. Small, reddish-brown to black, powdery 
pustules on the leaves. Control: If serious enough, spray as for Leaf Spots (above) , 
using zineb or maneb. 

14. Mistletoe — See (39) Mistletoe under General Diseases. 

15. Thread Blight — Southeastern states. See under Walnut. Control: Spray as for Leaf 
Spots (above) . 

16. Felt Fungus — Southeastern states. Purple-black, feltlike growth associated with 
scale insects. See under Hackberry. 

17. 2,4-D Injury — See under Grape. Dogwoods are very susceptible. 




Fig. 1 12. Spot anthracnose of dogwood. Spots on: A. Stem, B. Berries, C. Flower, D. Leaf. 



DYER'S GREENWEED 215 



DOLICHOS-See Pea 

DOUGLAS-FIR - See Pine 

DORONICUM — See Chrysanthemum 

DOXANTHA — See Trumpetvine 

DRABA — See Cabbage 

DRACAENA, CORDYLINE 

1. Leaf Spots, Tip Blight, Anthracnose — General. Round to irregular spots of various 
colors on the leaves. Centers of spots may be sprinkled with black dots. The 
lower and center leaves may die back from the tips. See Figure 113. If severe, all 
leaves may wither and die except a few leaves at the top of the plant. Control: 
Keep water off the foliage. Destroy infected leaves when first seen. If necessary, 
apply zineb, maneb, copper, or captan sprays, at 7- to 10-day intervals during rainy 
weather. 

2. Chlorosis — Plants yellowish and sickly. Most prevalent on poorly drained acid or 
alkaline soils. Control: Spray weekly for a month using iron sulfate or an iron 
chelate, following the manufacturer's directions. Plant in well-drained soil which 
is nearly neutral (about pH 6.5 to pH 7.2) . 

3. Gray-mold Blight — May cause extensive soft brown rotting in damp periods. Af- 
fected areas are covered with a coarse grayish mold. Control: Same as for Leaf Spots 
(above) . 

4. Root Rot — See (34) Root Rot under General Diseases. 

5. Root-knot — See (37) Root-knot under General Diseases. 

6. Stem Rot — Leaves turn yellow starting at the base of the stem. Plants wilt. The 
lower part of the stem is rotted, black, and water-soaked. Control: Plant disease-free 
stock or tip cuttings in clean or sterilized soil (pages 437-44) . Watering with zineb, 
captan, thiram, or ferbam (1 tablespoon per gallon) during rooting may be 
beneficial. 

7. Root-feeding Nematodes (lance, sheath) — Plants may appear sickly and gradually 
decline. May be associated with Root Rot. Control: Same as for Root Rot and Root- 
knot (both above) . 

DRACOCEPHALUM, DRAGONHEAD - See Salvia 

DRAGONROOT-See Calla 

DROPWORT-See Rose 

DRYOPTERIS - See Ferns 

DUCHESNEA-See Rose 

DUSTY - MILLER - See Chrysanthemum 

DUTCHMANS-BREECHES - See Bleedingheart 

DUTCHMANS-PIPE - See Aristolochia 

DWARF LACEPLANT - See Silver Lacevine 

DYER'S GREENWEED - See Broom 




Fig. 113. Dracaena tip blight. 



ELM 



217 



DYSCHORISTE - See Clockvine 

ECHEVERIA - See Sedum 

ECHINACEA — See Chrysanthemum 

ECHINOCACTUS - See Cactus 

ECHINOCYSTIS - See Cucumber 

ECHINOPS — See Chrysanthemum 

EGGPLANT -See Tomato 

ELAEAGNUS — See Russian-olive 

ELDER — See Snowberry 

ELECAMPANE — See Chrysanthemum 

ELEPHANTS-EAR - See Calla 

ELM [AMERICAN (many horticultural varieties), CEDAR, CHINESE, 

CHRISTINE BUISMAN, DUTCH, ENGLISH, HYBRID, JAPANESE, MOLINE, 

RED or SLIPPERY, ROCK or CORK, SCOTCH, SIBERIAN or DWARF, 

SMOOTH-LEAVED EUROPEAN, WEEPING, WINGED or WAHOO, WYCH ] 

(Ulmus); JAPANESE ZELKOVA (Zelkova) 

I.Dutch Elm Disease — Roughly the eastern half of the United States and spreading 
westward. Serious. Leaves wilt, often turn yellow to brown, curl, and usually drop 




Fig. 114. Dutch elm disease. Note shep- 
herd's crook and cut twig showing dark 
discoloration in the outer sapwood. The 
causal fungus makes the water-conducting 
tissue nonfunctional. 



early on one or more branches. Twig tips may curve downward to form "crooks." 
Branches die back. Entire trees may die in 1 to 2 months; others survive 1 to 3 
years or longer. A brown to black discoloration occurs in the white sapwood just 
under the bark in wilting branches. Positive identification is possible only through 
laboratory culturing. See Figure 114. Control: A community-wide program is 
needed in threatened areas. Remove and burn all dead and dying elm trees as 
soon as found. Clean up and burn all dead elm wood (with tight bark) in trees 
or on ground before trees leaf out in early spring. Debark stumps and fireplace 
wood. Repair and paint tree wounds promptly. Keep trees growing vigorously by 
proper watering and fertilizing. A single dormant spray of DDT is recommended 



218 ELM 

in many areas where the disease is present. Check with your park department, city 
arborist or forester, local arborist or county agent. The DDT spray kills the bark 
beetles which transmit the Dutch elm disease fungus. Beetles are spread long dis- 
tances by road and rail traffic. Resistant elms: Christine Buisman, Chinese, Siber- 
ian, Hybrid, and European Field. These trees are not immune to the disease. In- 
fected trees cannot be saved or cured. 

2. Phloem Necrosis — Serious in the eastern and central United States below 40° North 
latitude. During June and July, leaves roll upward, turn yellow, wither, and 
fall starting throughout the upper crown. Foliage is thin. Trees showing symptoms 
usually drop their leaves and die within a month or two. The inner bark, especially 
that near the base of the trunk, is often butterscotch-colored, sometimes flecked 
with brown or black. When such bark is warmed in a tightly closed jar, an "oil of 
wintergreen" odor is often evident. Roots die first. Control: Chinese, Christine 
Buisman, and Hybrid elms are highly resistant or immune. Spray susceptible elms 
with DDT and malathion to control leafhoppers which transmit the virus. Two 
applications are usually made, 35 to 40 days apart. Check with your city forester, 
county agent, or extension entomologist regarding timing of sprays for your area. 
Infected trees cannot be saved or cured. 

3. Other Wilts, Diebacks (V erticillium , Doihiorella — Cephalosporium or Deutero- 
phoma) — Widespread. External and internal symptoms often closely resemble 
Dutch elm disease, but infected trees may live on for a number of years, slowly dying 
back and declining in health. Leaves may be dwarfed and yellowed. Sucker growth 
is common on the trunk and larger branches. Laboratory culturing is needed for 
positive diagnosis. Control: Remove and burn severely infected trees. On others, 
remove infected branches flush with the next larger limb or trunk. Disinfect prun- 
ing tools between cuts. Keep trees vigorous by fertilizing liberally, plus watering 
during dry periods. Spray as for Black Leaf Spot (below) . 

4. Black Leaf Spot — General, especially in wet seasons. Small, irregular, grayish spots 
on the leaves. Later the spots become shiny and black. Infected leaves often turn 
yellow or brown and drop early in large numbers. See Figure 115. Trees vary greatly 
in susceptibility. Twigs may die back. Control: Collect and burn fallen leaves. 
Where practical, spray as the leaves unfold, and repeat 2 and 4 weeks later. Apply 
fixed copper, dichlone, zineb, phenyl mercury, or ferbam, plus spreader-sticker. 

5. Anthracnose, Leaf Spot, Twig B Ugh t — General. Irregular, brown spots or dead 
areas in leaves between the veins and margins. Twigs may die back. Control: Same 
as for Black Leaf Spot (above) except spray as the buds break open, 7 and 14 days 
later. 

6. Wetwood, Slime Flux — Widespread and common. Asiatic elms are very susceptible. 
Fermenting, dark-colored sap flows down from a branch stub, split crotch, or other 
bark wound, especially in the spring or following wet weather. The sap dries to 
form a light grayish-tan stain on the trunk and larger branches. See Figure 116. 
On young trees, the leaves on one or more branches may wilt, curl, turn color, and 
drop early. Branches on older trees die back gradually and the foliage is a sickly 
yellow color. Trees gradually decline in health. Often associated with wet soil, 
mechanical damage to the roots, branches, trunk and crotches, or to frost cracks. 
Control: Fertilize and water to stimulate vigor. Prune out dead and weak branches. 
Repair bark wounds promptly (page 22) . Cover with tree wound dressing. Check 
with a good tree surgeon. Trees may need cabling, bracing, or drain pipes installed. 

7. Twig Blights, Diebacks, Cankers — Widespread. Twigs and branches die back from 
cankers (bark often discolored or shows small, coral-pink to black "pimples" on the 
surface) . May follow winter, drought, or insect injury. Leaves on affected branches 
are often dwarfed or wilt later in the summer. Control: Prune out and burn dead 



ELM 



219 







flit? 
«ifn 



.:■-■■■' 

uxtttai 

Fig. 116. Wetwood or slime flux of elm. 



Fig. 1 15. Black leaf spot of elm. 



twigs and branches. Make cuts several inches beyond any visible sign of infection. 
Paint wounds promptly with a good tree wound dressing. Fertilize and water to 
maintain tree vigor. 

8. Wood Rots, Heart Rots — Cosmopolitan. See under Birch, and (23) Wood Rot 
under General Diseases. 

9. Root Rot — Trees gradually decline in vigor. Foliage is thin and sickly. Leaves 
may turn yellow, wither, and fall early. May be associated with nematodes. Control: 
See under Apple. 

10. Winter Injury, Sunscald, Frost Crack, Winter Drying — Twigs and branches may 
die back from the tips. Dwarfed, sickly leaves may unfold on affected branches and 
then die. In the spring limbs fail to leaf out. Freezing Injury: Inner bark may be 
water-soaked at first and then very dark. Several or all limbs may die. Long, up- 
and-down cracks (Frost Cracks) or large, dead, discolored areas (Frost Cankers) 
may form on the exposed south or southwest side of the trunk and larger limbs. 
Control: Water trees during dry periods, especially in a dry fall. Keep the crown 
of the tree pruned open. Fertilize in the spring. Wrap young trees with burlap, 
sisalkraft paper or otherwise shade from winter sun. See Figure 12. 

11. Mosaic, Mottle-leaf — General. Infected leaves are abnormally large or small. Leaves 
stiff, often distorted. Dwarfed leaves are usually mottled light green and yellow. 



220 EMILIA 

Witches'-brooms may form on twigs. Tree gradually lose vigor over a period of 
years. Foliage appears thinner and branches die back. Control: Where practical, 
replace with virus-free trees. No control is known. 

12. Physiological Leaf Scorch — Browning or scorching of leaves between the leaf veins, 
along the margins, or both places following hot, dry, windy weather in July and 
August. Control: Fertilize and prune out trees to increase vigor. Water during 
summer dry periods. 

IS. Bleeding Canker — Northeastern states. See under Beech and Maple. 

14. Leaf Blister — Small, grayish-white blisters on thickened, puckered leaves. These 
leaves may later turn yellow and drop early. Control: Same as for Anthracnose 
(above) . 

15. Powdery Mildews — General. White, powdery mold patches on leaves. Leaves may 
later shrivel. Control: If serious enough, spray twice, 10 days apart, using Karathane 
or sulfur. 

16. Root-knot — Elm is highly susceptible. See under Peach, and (37) Root-knot under 
General Diseases. 

17. Sooty Mold — Black, sooty mold grows in "honeydew" produced by aphids and 
scale insects. Control: Not necessary. Spray with DDT and malathion to control 
elm insects. 

18. Seed Rot, Seedling Blight — See under Pine. 

19. Virus Scorch of American Elm (southeastern states) —Elm leaves appear scorched 
at the margins and between the veins. Growth is stunted. Trees decline in vigor 
and the crown gradually dies back. Later the tree dies. Control: Check with your 
city arborist or park department. Destroy infected trees. Seek out virus-free stock 
from a reliable nursery. 

20. 2,4-D Injury — Elms are very susceptible. See under Grape. 
2\. Mistletoe — See (39) Mistletoe under General Diseases. 

22. Thread B Ugh t — Southeastern states. See under Walnut. 

23. Other Root-feeding Nematodes (dagger, lance, ring, spear, spiral, stylet or stunt, 
stem) — Often associated with sickly, unthrifty trees. See under Peach. 

24. Chlorosis — See under Maple. Occurs in alkaline soils. 

EMILIA — See Chrysanthemum 
EMPRESS-TREE - See Paulownia 
ENCELIA — See Chrysanthemum 

ENDIVE — See Lettuce 

ENGELMANN IVY - See Grape 

ENGLISH DAISY -See Chrysanthemum 

ENGLISH IVY -See Ivy 

EPIDENDRUM - See Orchids 

EPIGAEA-See Heath 

EPIPHYLLUM - See Cactus 

EPISCIA - See African-violet 

ERANTHEMUM - See Clockvine 

EREMOCHLOA - See Lawngrass 



EVENING-PRIMROSE 221 



ERICA -See Heath 

ERIGERON — See Chrysanthemum 

ERIOBOTRYA-See Apple 

ERODIUM-See Cranesbill 

ERYNGIUM, ERYNGO-See Celery 

ERYSIMUM -See Cabbage 

ERYTHRINA - See Honeylocust 

ERYTHRONIUM, DOGSTOOTH-VIOLET, YELLOW ADDERSTONGUE, 
TROUTLILY, FAWN LILY, ADAM-AND-EVE (Erythronium) 

1. Leaf Spot, Leaf Blight, Black Spot — Small specks or spots on the leaves. Leaves 
may later turn yellowish, wither, and collapse. Control: Pick off and burn spotted 
or blighted leaves when first noticed. 

2. Leaf Smuts — Widespread. Large, blister-like swellings on the leaves which break 
open to release brownish-black, powdery masses. Leaves may crack open and die. 
Control: Same as for Leaf Spot (above) . 

3. Botrytis Blights — See (5) Botrytis Blight under General Diseases. 

4. Rust — Western states. See (8) Rust under General Diseases. 

ESCAROLE-See Lettuce 

ESCHSCHOLTZIA - See Poppy 

EUCHARIS-See Daffodil 

EUONYMUS - See Bittersweet 

EUPATORIUM — See Chrysanthemum 

EUPHORBIA - See Poinsettia 

EUROPEAN CRANBERRY-BUSH - See Viburnum 

EUSTOMA-See Gentian 

EVENING-PRIMROSE [COMMON, WHITE], MISSOURI PRIMROSE, 
SUNDROPS, GOLDENEGGS (Oenothera); CALIFORNIA FUCHSIA, FIRE- 
CHALICE (Zauschneria) 

1. Rusts — General. Yellow-orange or reddish-brown, powdery pustules, mostly on 
underleaf surface. See (8) Rust under General Diseases. Alternate hosts include 
wild grasses and sedges (Aristida, Distichlis, and Carex spp.) . 

2. Powdery Mildew — General. See (7) Powdery Mildew under General Diseases. 
Usually causes little injury. 

3. Leaf Spots, Leaf Gall, Anthracnose — Round to irregular, variously colored spots, 
often with a dark margin. If severe, leaves may wither and drop early. Control: 
Collect and burn infected leaves. Apply zineb, several times, 10 days apart, starting 
when spotting is first evident. 

4. Downy Mildew — Widespread. See (6) Downy Mildew under General Diseases. 

5. Root Rots — See (34) Root Rot under General Diseases. 

6. Mosaic — See (16) Mosaic under General Diseases. 

7. Stem Nematode — See under Phlox. 



222 EVERLASTING 

EVERLASTING — See Chrysanthemum 

EXACUM-See Gentian 

FAGUS-See Beech 

FALL-DAFFODIL - See Daffodil 

FALSE - ACACIA - See Honeylocust 

FALSE - CAMOMILE — See Chrysanthemum 

FALSE - DRAGONHEAD - See Salvia 

FALSE - GARLIC - See Onion 

FALSE - INDIGO (Baptisia); LEADPLANT, INDIGOBUSH (Amorpha); 
INDIGO (Indigofera) 

1. Leaf Spots — Widespread. Spots of various sizes, shapes, and colors on the leaves. 
Control: Collect and burn tops in the fall. Apply zineb, maneb, or fixed copper at 
7- to 10-day intervals during rainy periods in the spring and early summer. 

2. Powdery Mildews — Common. White, powdery mold patches on the leaves. Control: 
Apply sulfur or Kara thane twice, 10 days apart. 

3. Rusts — General. Small, yellowish to orange spots and pustules on the leaves. In- 
fected leaves may drop in large numbers. Control: Same as for Leaf Spots (above) . 

4. Root Rots — See (34) Root Rot under General Diseases. May be associated with 
root-feeding nematodes (e.g., burrowing) . 

5. Twig Canker (amorpha) —See under Maple. 

FALSE -MALLOW -See Hollyhock 

FALSE- MESQUITE -See Calliandra 

FAREWELL - TO - SPRING - See Fuchsia 

FAWN LILY -See Erythronium 

FEIJOA-See Myrtle 

FELICIA — See Chrysanthemum 

FENDLERA-See Hydrangea 

FENNEL -See Celery 



FERNS 223 

FERNS: MAIDENHAIR (Adiantum); BIRDSNEST, SPLEENWORT (Asplenium); 

LADY, SILVERY SPLEENWORT (Athyrium); BLECHNUM; WALKING or 

WALKINGLEAF (Camptosorus); ROCKBRAKE or PARSLEY (Cryptogram ma); 

HOUSE HOLLY (Cyrtomium); BLADDER, BERRY BLADDER, BRITTLE 

(Cystopteris); HAY - SCENTED or BOULDER (Dennstaedtia); LEATHER WOOD 

or MARGINAL, MALE, MARSH or MEADOW, NARROW BEECH, OAK, 

SHIELD, TOOTHED WOOD, WOOD, (Dryopteris); BARROW, BOSTON, 

FLUFFY and GREEN RIPPLES, PERSON, SCOTT, SWORD, WHITMAN 

(Nephrolepis); SENSITIVE (Onoclea); ADDERSTONGUE (Ophioglossum); 

CINNAMON, INTERRUPTED, ROYAL (Osmunda); CLIFFBRAKE (Pellaea); 

COMMON POLYPODY or WALL, HARESFOOT, POLYPODY, RESURRECTION, 

ROCK POLYPODY (Polypodium); CHRISTMAS or DAGGER, GIANT HOLLY, 

LEATHER HOLLY, PACIFIC CHRISTMAS or WESTERN SWORD (Polystichum); 

AMERICAN OSTRICH or OSTRICH (Pteretis); BRACKEN (Pteridium); BRAKE 

or SPIDER (Pteris); WOODSIA, ROCK (Woodsia); CHAIN (Woodwardia) 

1. Anthracnose, Tip B Ugh t — Growing tips of leaves (fronds) turn brown, shrivel, 
and die. Plants appear sickly and blighted. Control: Remove and burn blighted 
fronds. Destroy badly infected plants. If possible, avoid sprinkling the foliage. In- 
doors, regulate the temperature, humidity, and ventilation. Avoid overwatering. 

2. Leaf Spots, Leaf Blight, Tar Spot — Fronds have spots of various colors and sizes, 
especially at or near the margins. Spots may be zoned or run together, forming 
large blotches. Leaves may roll and wither prematurely. Control: Same as for 
Anthracnose (above) . 

3. Leaf Nematodes — Symptoms variable. Reddish-brown to black bands, limited by 
the leaf veins. Often extend from the center to the margin of a leaf. Or irregular 




Fig. 117. Leaf nematode of fern. 

blotches may occur (Figure 117). On birdsnest fern, the base of the frond turns 
brown. Later the discoloration moves upward. Plants may die. Control: Remove 
and burn infested leaves. Indoors, keep water off the foliage. Birdsnest and similar 
ferns may be disinfested by immersing the plants in hot water (110° F.) for 10 to 
15 minutes. 

4. Rusts — Primarily an outdoor problem. Reddish-brown to black, powdery pustules, 
arranged irregularly on the fronds. Most common near the alternate hosts (alpine, 
balsam, grand, noble, Pacific silver, and lowland white firs) . Control: None usually 
needed. 

5. Leaf Blisters, Leaf Gall — Well-marked yellow areas on both leaf surfaces. Control: 
None usually needed. Same as for Anthracnose (above) . 

6. Leaf Scorch — Tips and margins of leaves are scorched. Fronds tend to die back. 
Control: Avoid excessive sun and wind. Plant in a shady spot in natural, moist 
"woods soil." 



224 FERN 

7. Sooty Mold, Black Mildew — Black mold grows on leaf surface following scale or 
other insects. Control: Destroy insects, using malathion sprays or dips. 

8. Damping-off — Seedlings (prothallia) become soft and dark and collapse. Control: 
Sow fern spores in a sterile rooting medium such as soil or sifted sphagnum moss. 

9. Inflorescence Smut (osmunda) —See (11) Smut under General Diseases. 

FERN, ASPARAGUS or LACE - See Asparagus 

FEROCACTUS - See Cactus 

FESCUE, FESCUE GRASS (Festuca) - See Lawngrass 

FETTERBUSH - See Blueberry 

FEVERFEW — See Chrysanthemum 

FIG [COMMON, CREEPING, FIDDLELEAF, FLORIDA STRANGLER], 

INDIA RUBBER TREE, RUBBER PLANT (Ficus); 

PAPER - MULBERRY (Broussonefia) 

1. Anthracnose, Leaf Spots, Fruit Rot — General. Tips and margins of leaves are 
yellowish, then tan, and finally dark brown and "scorched." Minute pinkish 
"pimples," sometimes in zones, may be sprinkled in diseased areas. Enlarging, 
sunken, discolored spots on fig fruit. Control: Pick off and burn infected leaves. In 
a commercial fig-growing area, check with your county agent or extension plant 
pathologist regarding a suitable spray program. Indoors, avoid sprinkling the 
foliage. If practical, apply zineb or captan before wet periods. 

2. Leaf Scorch, Leaf Roll, Leaf Fall — Primarily an indoor problem. Tips and margins 
of leaves are scorched. Or large blotches occur in the leaves. Affected areas may 
curl and crack. Leaves drop early. Control: Keep the soil at a uniform moisture 
level. Avoid high room temperatures and exposure to full sun. Do not keep the air 
too dry. Repot plants using a light, fast-draining potting mixture. 

3. Crown Gall — See under Begonia, and (30) Crown Gall under General Diseases. 

4. Root Rots — See under Apple, and (34) Root Rot under General Diseases. May be 
associated with nematodes (e.g., burrowing, dagger, fig cyst, pin, root-lesion or 
meadow, ring, root-knot, spiral, stubby-root, stylet or stunt) . Control: Destroy badly 
infected indoor plants and replant in sterilized soil (pages 437-44) . 

5. Dieback, Canker, Twig Blights, Limb Blight — See under Maple. Prune plants 
carefully late in the season and remove all dead branches, cankers, and dried-up 
fruit. Dip pruning shears in 70 per cent denatured alcohol, 1:1,000 mercuric chlo- 
ride, or phenyl mercury solution after each cut through a canker. Paint all cuts 
with tree wound dressing (page 25) . Spray as for Rust (below) . Protect trees 
against winter injury. See under Apple. 

6. Fruit Rots, Souring (fig) — Rot spots of various colors develop in the fruit. Black, 
gray, or pink mold may grow on affected areas. Control: Pick fruit as soon as ripe. 
Collect and destroy dropped fruit promptly. 

7. Other Leaf Spots, Leaf Blotch, Rusty Leaf— Spots and streaks of various colors, 
sizes, and shapes on leaves. Spots may enlarge until the entire leaf is blighted. 
Control: Same as for Anthracnose (above) and Rust (below) . 

8. Sooty Mold — See under Apple, and (12) Sooty Mold under General Diseases. 

9. Rust (fig) — Numerous small, reddish to brownish spots on underleaf surface. If 
severe, leaves may turn yellowish-brown and drop early. Control: Apply ferbam, 
fixed copper, or bordeaux mixture at 2- to 3-week intervals. 

10. Root-knot, Fig Cyst Nematode — A limiting factor in fig production. See under 



FLAX 225 

Peach, and (37) Root-knot under General Diseases. Fumigate soil with D-D, EDB, 
Nemagon, Fumazone, or VC-13. Fig species are available which are resistant root- 
stocks. 

11. Wood Rots (fig) —See under Birch, and (23) Wood Rot under General Diseases. 

12. Mosaic (fig) — Symptoms variable. Leaves may be severely distorted, show irregular, 
yellowish-green blotches, spots, bands, or yellowish mottling. Fruit may be deformed 
and spotted. Both fruit and leaves may drop early. Transmitted by grafting and 
mites. Control: Plant virus-free stock. Destroy infected plants when found. Varie- 
ties differ considerably in resistance. Check with your county agent or extension 
plant pathologist. 

13. Sunscald, Winter Injury — See under Apple and Elm. Disease organisms get into 
frost-weakened and sunburned trees. Control: Whitewash or wrap trees (page 29) . 

14. Oedema (rubber plant) —Indoor problem. Corky callus-growths on the petioles 
and underleaf surface. Control: Increase light and temperature and decrease soil 
moisture, especially in humid weather. 

15. Fusarium Wilt (fig) —See (15A) Fusarium Wilt under General Diseases. 

16. Mistletoe (paper-mulberry) —See (39) Mistletoe under General Diseases. 

17. Web Blight, Thread Blight — Southeastern states in warm, moist weather. White, 
threadlike, fungus hyphae grow over the underleaf surface killing the leaves, many 
of which remain hanging on the tree matted together by the spiderweblike fungus 
threads. See also under Bean. Control: Apply one or two sprays of fixed copper or 
bordeaux. Pruning out of infected branches may be warranted. 

18. Southern Blight — See (21) Crown Rot under General Diseases. 

19. Chlorosis, Zinc and Manganese Deficiency — See under Walnut. 

FIGMARIGOLD - See Iceplant 
FILBERT -See Birch 
FIUPENDULA-See Rose 
FINOCCHIO-See Celery 
FIR — See Pine 
FIRE - CHALICE — See Evening - primrose 
FIRECRACKER PLANT - See Cigarflower 
FIRE -PINK -See Carnation 
FIRETHORN-See Apple 
FIREWHEEL - See Chrysanthemum 
FIRMIANA — See Phoenix - tree 
FITTONIA-See Silver Threads 
FIVE -LEAF or FIVE - FINGERED ARALIA-See Acanthopanax 
FLAME VIOLETS - See African - violet 
FLANNEL - BUSH - See Phoenix - tree 
FLAX, FLOWERING [ ANNUAL, BLUE, GOLDEN ] (Linum) 
1. Stem Rot, Damping-off — Seedlings wilt and collapse. Stems rot off at the soil line. 
May be covered with a cottony mold. Control: Treat seed with captan, thiram, or 
chloranil. Avoid overwatering, overcrowding, and planting in poorly drained soil. 



226 FLEABANE 

Dig up and burn older, dying plants together with several inches of surrounding 
soil. 

2. Root-knot — See under Bean, and (37) Root-knot under General Diseases. 

3. Curly-top — See (19) Curly-top under General Diseases. 

FLEABANE, FLORAS - PAINTBRUSH - See Chrysanthemum 

FLORIDA YELLOWTRUMPET-See Trumpettree 

FLOWERING ALMOND -See Peach 

FLOWERING CRABAPPLE - See Apple 

FLOWERING CURRANT -See Currant 

FLOWERING MAPLE - See Hollyhock 

FLOWERING QUINCE - See Apple 

FLOWERING TOBACCO - See Tomato 

FLOWER -OF -AN -HOUR -See Hollyhock 

FOAMFLOWER - See Hydrangea 

FOENICULUM-See Celery 

FOGFRUIT-See Lantana 

FORESTIERA - See Ash 

FORGET - ME - NOT - See Mertensia 

FORSYTHIA [ EARLY, GOLDENBELLS, KOREAN, SPRING GLORY, WEEPING ] 

(Forsythia) 

l.Leaf Spots, Anthracnose — Small to large, grayish, yellow, or brown spots on the 
leaves. Control: Pick off and burn infected leaves. If necessary, apply zineb or 
maneb several times, 10 days apart. 

2. Twig or Cane Blight, Dieback, Southern Blight, Blossom B Ugh t — Blossoms turn 
brown. Twigs wither and die back from girdling cankers or a crown rot. A dense 
cottony mold may grow over the plant near the soil line. Control: Prune and burn 
infected twigs. Keep the soil surface at the crown loose and dry. Applying Terraclor 

(PCNB) as a dust or spray to the crown may help. See under Bean, White Mold. 

3. Bacterial Blight — Shoots and entire branches may blacken and die. Brown stain in 
the wood. Often throughout a whole branch. Control: See under Lilac. 

4. Stem Gall — Round to irregular, bunchy overgrowths along the stems. Stems un- 
sightly in winter. May die back. Control: Cut off and burn infected branches. 

5. Crown Gall — See under Apple, and (30) Crown Gall under General Diseases. 

6. Root-knot — Forsythia is quite susceptible. See (37) Root-knot under General 
Diseases. 

7. Root Rot — See (34) Root Rot under General Diseases. May be associated with 
root-feeding nematodes (e.g., dagger, ring, root-knot, stem, stylet or stunt) . 

FORTUNELLA-See Citrus 



FROELICHIA 227 



FOUR -O'CLOCK [COMMON, COLORADO] (Mirabilis); TRAILING FOUR- 
O'CLOCK (Allionia); SAND -VERBENA (Abronia); UMBRELLAWORT 

(Oxybaphus) 

1. Rusts (four-o'clock, sand-verbena, trailing four-o'clock) — Southwestern states. 
Small, yellow or yellowish-orange spots on the leaves. Alternate hosts may include 
wild grasses (Aristida and Distichlis). Control: If serious, apply zineb or maneb 
about 10 days before rust normally appears. Repeat sprays at 10-day intervals. 

2. White-rust — Pale yellow spots on the upper leaf surface with white pustules on the 
corresponding underside. Control: Collect and burn tops in the fall or spotted 
leaves as they appear. Spray as for Rusts (above) . 

3. Leaf Spots — Small and indistinct or round, pale brown to tan spots, with dark 
borders, on the leaves. Control: Pick off and burn spotted leaves. Spray as for Rusts 
(above) . 

4. Root-knot — See under Bean, and (37) Root-knot under General Diseases. 

5. Curly-top (four-o'clock) —Western states. See under Beet, and (19) Curly-top 
under General Diseases. 

6. Root Rot — See (34) Root Rot under General Diseases. 

7. Downy Mildew (four-o'clock, sand verbena, trailing four-o'clock, umbrellawort) - 
See (6) Downy Mildew under General Diseases. 

FOXGLOVE — See Snapdragon 

FRAGARIA — See Strawberry 

FRAGRANT GLAD -See Gladiolus 

FRAGRANT PINK -See Carnation 

FRAGRANT STOCK -See Cabbage 

FRAGRANT VIBURNUM -See Viburnum 

FRANGIPANI-See Oleander 

FRANKLIN - TREE, LOBLOLLY - BAY (Franklinia, Gordonia) 

l.Leaf Spot — Small spots on leaves. Control: If serious enough, spray with zineb, 
maneb, or fixed copper in wet seasons. 

2. Black Mildew — Southern states. Black, moldy spots or blotches on the leaves. 
Control: Same as for Leaf Spot (above) . Control insects with malathion sprays. 

3. Root Rot — See (34) Root Rot under General Diseases. 

PRASERA-See Gentian 

FRAXINUS-See Ash 

FREESIA-See Gladiolus 

FREMONTIA — See Phoenix-tree 

FRENCH-MULBERRY - See Lantana 

FRINGETREE - See Ash 

FRITILLARIA, FRITILLARY - See Tulip 

FROELICHIA - See Cockscomb 



228 FROSTWEED 

FROSTWEED, FROSTWORT - See Sun-rose 

FUCHSIA; ROCKY MOUNTAIN GARLAND (Clarkia); BOISDUVALIA, SPIKE- 
PRIMROSE (Boisduvalia); FAREWELL-TO-SPRING, SATIN-FLOWER (Godetia) 

1. Rusts — Pale spots on the upper leaf surface and yellowish-orange or brown to 
black, powdery pustules on the lower leaf surface. Lower leaves may shrivel and 
die. Control: Pick off and burn infected leaves. If serious enough, apply zineb, fer- 
bam, maneb, or dichlone at weekly intervals. 

2. Gray-mold Blight, Stem Canker — Leaves blighted and covered with a dense gray 
mold. See (5) Botrytis Blight under General Diseases. Control: Avoid overcrowding. 
Increase air circulation and reduce humidity. 

3. Verticillium Wilt — See (15B) Verticillium Wilt under General Diseases. 

4. Root-knot — See under African-violet, and (37) Root-knot under General Diseases. 

5. Root Rots — Plants may wilt suddenly and die within a few days. See (34) Root 
Rot under General Diseases. 

6. Spotted Wilt — See under Begonia, and (17) Spotted Wilt under General Diseases. 

7. Damping-off — Seedlings collapse from a rot at the soil line. Control: Grow seedlings 
in sterilized soil (pages 437-44) or in a sterile medium. 

8. Clarkia Stem Rots, Fusarium Wilt — See under Chrysanthemum. 

9. Aster Yellows, Curly-top (clarkia, godetia) — See under Chrysanthemum. 
10. Downy Mildew (clarkia, godetia) —See under Chrysanthemum. 
W.Leaf Spots, Anthracnose (clarkia) —See under Chrysanthemum. 

FURCRAEA — See Centuryplant 

GAILLARDIA — See Chrysanthemum 

GALANTHUS-See Daffodil 

GALAX; OCONEE-BELLS (Shortia) 

l.Leaf Spots — Small to large, round to irregularly lobed spots and blotches on the 
leaves. Leaves may wither and die early. Control: Pick off and burn spotted leaves. 
Do not syringe plants. If needed, spray several times at weekly intervals. Use zineb, 
maneb, or dichlone. 

GALIUM -See Buttonbush 

GALTONIA-See Tulip 

GARDEN BALSAM -See Balsam 

GARDEN CRESS -See Cabbage 

GARDEN-HELIOTROPE (Valeriana) - See Valerian 

GARDEN HUCKLEBERRY - See Blueberry 

GARDEN VERBENA -See Lantana 

GARDENIA, CAPE-JASMINE (Gardenia) 

l.Stem Canker or Gall — Widespread. Primarily an indoor problem. Leaves dwarfed, 
wilt, shrivel, turn yellow and fall early. Flower buds are blasted and fall before 
opening. Oblong, sunken to swollen, brown cankers form on the branches and at 
the crown. May girdle affected parts causing stunting and death. Crown cankers 



GARDENIA 



229 



appear as corky overgrowths (swollen, cracked ridges). See Figure 118A. Control: 
Buy disease-free plants or take tip cuttings from healthy plants. Use a sharp knife. 
Avoid injuring plants. Remove cankers on branches by cutting stems 3 inches back 
of the cankers. Swab cuts immediately with 70 per cent denatured alcohol. Remove 
and burn severely infected plants. Keep water off the foliage. Place new plants in 
another location. Dip cuttings in ferbam (2 tablespoons per gallon) , Semesan, or 



Fig. 118. A. Stem canker of gardenia, 
Leaf spots of gardenia. 




phenyl mercury solution (1 ounce in 5 gallons) for 5 minutes before sticking. Use 
a pasteurized rooting medium (pages 437-44) . Spray stems and crowns weekly using 
zineb or ferbam. Veitchii is more resistant to Phomopsis Canker than Belmont or 
Hadley. 

Fungus Leaf Spots — Round to oval spots, sometimes zoned. Mostly on the lower 
leaves following wet weather. Leaves may die. See Figure 118B. Control: Pick off 
and burn infected leaves. Space plants. Avoid sprinkling water on the foliage and 
wounding leaves. Spray foliage as for Stem Canker (above) . Use disease-free plants 
for propagation. Varieties differ in resistance. 

Bacterial Leaf Spot — Small to large, round to angular, brown or reddish-brown 
spots on the leaves, surrounded by a narrow, water-soaked or yellowish border. 
Leaves may turn yellow and drop early, starting at the base of the plant. Control: 
Same as for Fungus Leaf Spots (above) . Plant only disease-free cuttings. Sterilize 
soil and containers before planting. See "Soil Treatment Methods and Materials" 
in the Appendix. 

Bud Rot, Bud Drop — Buds may turn pale green or yellow, often soften, darken, 
and drop. Flower stalks may be discolored. Control: Same as for Fungus Leaf Spots 
(above) . Indoors, avoid large temperature fluctuations, overwatering, and dry or 
extremely humid air. Add daytime lights during overcast periods. The tempera- 
ture should be about 62° to 65° F. at night and above 70° F. during the day. Pick 
off and burn affected buds. Increase humidity in the home. 

Root-knot — Widespread in southern states and northern greenhouses. Gardenia is 
highly susceptible. Leaves may wilt during the day; fall prematurely. Plants may be 
stunted with sickly, mottled leaves. Control: Dig up and burn infested plants. Plant 
in sterilized soil. Gardenia thunbergia is a resistant rootstock. 



230 GARLAND FLOWER 

6. Gray-mold Blight, Botrytis Petal Blight — Numerous, light brown spots on the pet- 
als which enlarge and run together forming blotches. A gray mold may grow on 
infected tissues in damp weather. Buds may drop early. Control: Same as for Fungus 
Leaf Spots (above) . Carefully pick off and burn blighted flowers and buds. If prac- 
tical, spray blooms at 2- or 3-day intervals in damp weather using a fine mist of 
captan or zineb (1 tablespoonful per gallon of water) . 

7. Chlorosis — Widespread. Leaves are stunted and pale green or yellowish between 
the veins. Young leaves may turn yellow, die, and fall early. Plants make poor 
growth. Tips may die. See Figure 79. Control: Plant in light, well-drained, slightly 
acid soil. Have the soil tested if in doubt. Keep plants free of Stem Canker and 
Root-knot. Have the soil above 60° F. Spray plants monthly with iron sulfate, 1 
tablespoon per gallon of water. Or apply iron chelate (or iron sulfate) to the 
soil in water solution. Follow the manufacturer's directions. 

8. Sooty Mold — Very common in the Gulf States following attacks by scales, white- 
flies, mealybugs, and other insects. Crusty black coating forms on leaves and stems. 
Control: Wash off the sticky coating. Apply malathion to control insects. 

9. Powdery Mildew — See (7) Powdery Mildew under General Diseases. 

10. Root Rot — See (34) Root Rot under General Diseases. Often associated with 
nematodes (e.g., burrowing, dagger, lance, needle, pin, reniform, ring, root-lesion, 
spiral, stubby-root, stylet or stunt) . 

11. Dieback — Indoor problem. Branches die back. Leaves wither and fall off. Con- 
trol: Avoid overwatering. Plant in well-drained soil. 

12. Crown Gall — See (30) Crown Gall under General Diseases. 

GARLAND FLOWER - See Daphne 

GARLIC - See Onion 

GARRYA — See Dogwood 

GAULTHERIA - See Heath 

GAYFEATHER - See Chrysanthemum 

GAYLUSSACIA - See Blueberry 

GAZANIA — See Chrysanthemum 

GELSEMIUM - See Butterflybush 

GENISTA — See Broom 

GENTIAN [CLOSED, FRINGED, NARROW-LEAVED] 

(Gentiana); PRAIRIEGENTIAN, TEXAS-BLUEBELL (Eustoma); 

EXACUM; COLUMBO (Frasera) 

l.Leaf Spots, Leaf Blotch — Spots of various colors, shapes, and sizes on the leaves. 
If severe, leaves may wither. Control: Pick off and burn spotted leaves. Spray at 
10- to 14-day intervals during wet periods, using zineb, maneb, or fixed copper. 

2. Botrytis Blight, Stem Canker (gentian, exacum) — Light brown spots or blotches 
on the leaves with darker margins. Cankers may form on the stems. A gray mold 
often covers infected areas in damp weather. Control: Remove and destroy in- 
fected parts. Space plants. Spray as for Leaf Spots (above) . 

3. Rusts (columbo, gentian) — Yellow spots on the lower leaves. Spots may later turn 
into reddish-brown, dark brown, or black powdery pustules. Disease moves upward 
as the season progresses. Control: Destroy infected plants. Spray remainder as for 
Leaf Spots (above) . 



GERANIUM 231 

4. Root and Crown Rot, Damp ing-off — Seedlings wilt and collapse. Older plants rot 
at the base. Roots often decay. Control: Plant in clean, well-drained soil. Rotate. 
Avoid overwatering and wounding stems and roots. 

5. Stem Blights (prairiegentian) -See (22) Stem Blight under General Diseases. 
Control: Spray as for Leaf Spots (above) . Add malathion to control mealybugs 
and other insects. 

6. Black Mildew (columbo) -See (12) Sooty Mold under General Diseases. 

GERANIUM [ FISH, FLORISTS', IVY, LADY WASHINGTON, NUTMEG, ROSE, 
STORKSBILL] (Pelargonium) (See also Cranesbill) 

1. Blackleg, Stem and Cutting Rots — Cosmopolitan. Leaves turn yellow or reddish 
and drop. Plants stunted. Die gradually. Base of cutting or stem is soft, brown, 
and water-soaked. Soon blackens, shrivels, and may turn slimy. Rot works upward 
from the soil line until plant wilts and dies. See Figure 37D under General Dis- 
eases. Control: Take only tip cuttings from disease-free plants sprayed 30, 20, and 
10 days before taking cuttings. Use ferbam, zineb, or captan (\i/ 2 tablespoons per 
gallon of water) . Plant in a sterile medium (pages 437-44) . Avoid overcrowding, 
overwatering, or sprinkling water on the foliage. Sterilize cutting knife and other 
tools by dipping in a 1:1,000 solution of mercuric chloride or 70 per cent de- 
natured alcohol between cuts. Keep down the humidity and increase the air cir- 
culation. Separate healthy from diseased plants. If rot starts in the cutting bed, 
remove infected plants or plant parts and apply zineb as a soil drench (2 table- 
spoons per gallon of water) . Destroy infected plants when first discovered. 

2. Root Rots — Leaves, especially the lower ones, turn yellow, wilt, die, and then 
fall off. New shoots are pale green and sickly. Flowering is reduced. Or blossoms 
fall soon after opening. Roots are brown or black and rotted. May be associated 
with nematodes (e.g., pin, root-knot, root-lesion, spiral, stem, stubby-root, stylet) . 
Control: Same as for Blackleg (above) . 

3. Crinkle, Mosaic, Mottle, Leaf Curl, Leaf Breaking, Spotted Wilt, Ringspots, Curly- 
top (Leaf Cupping?). — General. A virus complex producing variable symptoms 
which may disappear in hot weather. Leaves may be stunted, ruffled, crinkled, 
cupped inward, puckered, and dwarfed. Small, round to irregular, pale yellow to 
white, red or purple spots, rings or arclike patterns may appear on the leaves. Or 
leaves may be mottled with light and dark green areas. Normal leaf patterns tend 
to disappear. Leaves may turn yellow and drop early. Symptoms are most appar- 
ent on young leaves in cool weather. Plants stunted, may appear bushy. Flower- 
ing is reduced. Control: Take tip cuttings only from known virus-free plants. Dis- 
card plants which look suspicious. Varieties differ greatly in apparent resistance. 
Control insects and mites using malathion. 

4. Fungus Leaf Spots, Blossom Blight, Gray-mold Blight — Cosmopolitan. Small to 
large, round to irregular, spots on the leaves which are water-soaked, light brown 
to tan, reddish-brown or dark brown in color. Spots may enlarge and run together 
killing the leaf. Flower petals may discolor, fade, and wilt. Flowers fall prematurely. 
Affected parts may later be covered with an olive-green, gray, dark brown, or 
black mold. See figures 19A and 45C under General Diseases. Control: Same as 
for Blackleg (above) . Pick off and burn infected leaves and blossoms. Apply cap- 
tan, zineb, maneb, or fixed copper during damp periods. 

5. Bacterial Stem Rot (Wilt) and Leaf Spots — Often a limiting factor in production. 
Small, dark green, water-soaked blisters on the leaves. Mostly on underleaf sur- 
face. Spots enlarge, and often run together becoming angular with centers sunken 
and brown. May resemble "frogeyes." Leaves may turn yellow, wither, and fall. 
Infected stems are dull blackish-brown and shriveled with a semidry rot. Cuttings 



232 GERBERA 

rot progressively upwards from the base. Control: Same as for Blackleg (above) . 
Destroy infected leaves. Varieties differ in resistance. Avoid forcing plants too 
rapidly, especially during warm, humid weather. Space plants. Maintain balanced 
fertility. 

6. Oedema, Dropsy — Common indoor problem. Small, water-soaked leaf spots which 
later become reddish-brown, corky, and raised. Mostly on larger leaf veins but also 
occur on stems and petioles as corky ridges. Leaves may turn yellow and drop 
early. Control: During overcast, humid weather avoid overwatering. Lower the 
humidity and increase heat and light. Space plants. Avoid low potassium and 
calcium levels in the soil. 

7. Root-knot — Plants may be sickly and weak from small galls on the roots. Control: 
Destroy infested plants and grow new plants in sterilized soil. See pages 437-44 in 
the Appendix. Start with tip cuttings. 

8. Verticillium Wilt — Lower leaves turn yellow at the margins and wilt. Wilt later 
progresses up the stem. Plants may be stunted. Control: Destroy infected plants. 
Take only tip cuttings from healthy plants. Then treat as for Blackleg (above) . 

9. Crown Gall — Common but not very damaging. Cauliflowerlike galls or knots 
formed on the roots and crown. Growth is checked. Control: Take cuttings from 
healthy plants. Grow plants in sterilized soil. Avoid wounding stems. 

10. Leafy Gall, Fasciat i on — Plants stunted. Clusters of small, malformed shoots form 
near the soil line. May closely resemble Crown Gall. See Figure 42B under Gen- 
eral Diseases. Control: Same as for Crown Gall (above) . 

11. Leaf Nematode — See (20) Leaf Nematode under General Diseases. 

GERBERA, GERMAN CAMOMILE - See Chrysanthemum 

GERMANDER -See Salvia 

GERMAN IVY — See Chrysanthemum 

GESNERIA — See African - violet 

GEUM-See Rose 

GHERKIN, WEST INDIAN - See Cucumber 

GIANT DAISY — See Chrysanthemum 

GIANT WHITE NIGHT BLOOMER -See Morning-glory 

GILIA-See Phlox 

GINKGO, MAIDENHAIR -TREE (Ginkgo) 

l.Leaf Spots, A n thracnose — Uncommon. Yellow to brownish spots on the leaves. 
Leaves may turn yellow. Control: See Leaf Spots under Maple. 

2. Root-knot — See under Peach, and (37) Root-knot under General Diseases. 

3. Wood Rots — See under Birch, and (23) Wood Rot under General Diseases. 

4. Root Rot — See (34) Root Rot under General Diseases. 

GLADIOLUS [COMMON, MINIATURE, NIGHT - BLOOMING ] (Gladiolus); 

FRAGRANT GLAD (Acidanthera); COPPER - TIP (Crocosmia); CROCUS 

[SAFFRON, SPRING] (Crocus); FREESIA; IXIA; TIGERFLOWER, AZTEC LILY, 

SHELL FLOWER (Tigridia); MONTBRETIA (Tritonia) 

1. Corm and Bulb Rots, Crown Rot, Southern Blight, Flower Blights, Wilt, Yellows — 
General and serious. Leaves pale, turn yellow, wither, and die back from rotting 



GLADIOLUS 



233 



of crown or underground parts. Corm (or bulb) shows round to irregular, tan, 
yellowish-brown, reddish-brown, dark brown or black rotted areas which may be 
somewhat sunken. The whole corm may rot, becoming a dry, brownish-black 
"mummy." The rot often spreads up into the leaves which darken and rot at 
their bases. Infected corms continue to rot in storage, but may show no symptoms 
at the time of digging. A bluish-green, gray, black, or cottony mold growth may 



Fig. 119. Freesia corm rot. 




develop on rotted areas during storage. Flowers may be spotted and blighted. See 
Figure 47C under General Diseases and Figure 119. Control: Plant only best qual- 
ity, disease-free corms in sterilized soil (pages 437-44) or where disease has not 
occurred before. Grow in a sunny spot where air circulation is good. Avoid low, 
wet spots. Fertilize well with potassium and phosphorus but keep nitrogen on the 
low side. Dig and destroy infected plants as they occur. Gladiolus varieties differ 
greatly in resistance. Handle corms carefully to prevent bruising. Harvest corms 
(or bulbs) early, shake off loose soil, and cure rapidly at 75° to 90° F. with good 
ventilation, for 1 to 2 weeks. Then remove tops and roots and dust corms thor- 
oughly with thiram. Before treatment, sort and discard those showing rot spots. 
When treating, shake corms and dust together in a tight paper sack. For each 
quart of corms use an amount of dust at least equal in quantity to an aspirin tab- 
let. If using a dip, soak gladiolus corms in a 1:1,000 solution of mercuric chloride 
for 2 hours, New Improved Ceresan (1 tablespoon per gallon) for 15 minutes, or 
use Emmi or liquid Ceresan, following the manufacturer's directions. Certain 
varieties may be injured by these mercury treatments. Use with caution. Or soak 
dormant gladiolus cormels, kept in a warm dry room, in hot water (135° F.) for 30 
minutes. This treatment may reduce sprouting. Store corms over winter in a 
well-ventilated, cool (35° to 40° F. location with low humidity (about 75 per 
cent) . Applying Vapam, V.P.M. Soil Fumigant, or chloropicrin as a furrow or 
broadcast treatment, several weeks before planting, has proved beneficial. Follow 



234 



GLADIOLUS 



the manufacturer's directions. Terraclor applied in the open furrow at planting 
time has given good control of Stromatinia (Sclerotinia) Rot. Use \/ 2 pound of 20 
per cent dust for 22 feet of row. Keep down weeds. Burn all plant debris in the 
fall. In humid areas, spray as for Leaf Spots (below) . 
2. Bacterial Scab, Neck Rot, Bacterial Leaf Spot — General in warm wet weather, 
pale yellow to brownish-black, varnish-like spots or streaks form on the husks. 
Corm tissue underneath shows round, yellowish to tan, water-soaked spots which 
later become brownish-black, sunken, scabby, and gummy. Leaf bases (neck) may 
rot and the top collapses. Scabby corms are associated with bulb mites. Small, 
more or less round, reddish-brown, water-soaked leaf spots may enlarge and 
run together forming large dead blotches. Leaves may turn yellow at the tips and 
die prematurely. See Figure 120. Control: Same as for Corm Rots (above) . Plant 
only scab-free corms. Apply a soil insecticide (e.g., aldrin, dieldrin, or heptachlor) 



CORM SCAB 




NECK ROT 



Fig. 120. Bacterial scab of gladiolus. 

in the furrow before planting to control wireworms, other soil insects, and bulb 
mites. 

3. Bacterial Leaf Blight — May be serious in wet seasons. Water-soaked, dark green 
leaf spots which later turn brown. Spots become gummy and square or rectangu- 
lar in shape. Leaves appear scorched. May die. Spots restricted to between the 
leaf veins when young. Younger plants most severely attacked. Control: Soak 
corms in a mercury-containing solution. See Corm Rots (above) . 

4. Leaf Spots, Flower Spots or Blights— General. Small, round to elongated or ir- 
regular spots of various colors — tan, yellow, brown, purpish-brown or black — 
some with one or more dots or mold growth in the center. Leaves may turn yel- 
low, wither, and die back from the tips. Plants may not bloom. Corm size and 
production is often decreased. Spots also may occur on the corms, stems, bud 
sheaths, and flower petals. See Figure 45B under General Diseases, and Figure 121. 
Control: Same as for Corm Rots (above) . Spray weekly during moist weather 
using zineb, maneb, or captan plus spreader-sticker. Start when leaves are 6 to 10 
inches tall or when disease first appears. Varieties differ in resistance. Destroy tops 
after flowering. Commercial growers often dip flower spikes in a phenyl mercury 
solution, plus wetting agent, before shipping. 

5. Mosaics, White Break — Widespread. Plants may be stunted with mild to severe 
yellowish-green, spotted, mottled, or striped leaves. Infected plants may bloom 



GLORYVINE 235 



early with flower petals crinkled, deformed, and streaked, striped, or flecked with 
whitish, yellowish, or greenish blotches. See (16) Mosaic under General Diseases. 
One virus (Tobacco Ringspot) may be spread by cutting shears in harvesting 
flowers and corms or bulbs. Control: Dig and burn infected plants when first 
found. Keep down weeds. Control aphids which transmit the viruses. Use mala- 
thion. Plant virus-free corms or bulbs. Disinfect shears after cutting suspicious 
flowers or tops. 

6. Aster Yellows, Grassy-top — Symptoms greatly variable. Young leaves may turn 
yellowish-green and be twisted. Flower spike may be spindly, green, and twisted. 
Plants may mature and die early. Often produce small corms and no color in the 
flowers. Control: Same as for Mosaics (above) . Control leafhoppers which trans- 
mit the virus, using DDT and malathion at about weekly intervals. 

7. Root Rot, Neck or Collar Rot — Plants may wilt, collapse, and die. Easily pulled 
up. Leaf bases and roots are often rotted under wet soil conditions. Plants often 
killed out in a section of row. May be associated with nematodes (see below) . 
Control: Same as for Corm Rots (above) . A soil drench of Terraclor or Botran 
(Upjohn) plus Nemagon or Fumazone in infested areas may help. Start when 
disease is first evident. 

8. Root-feeding Nematodes (e.g., pin, root-knot, root-lesion, sheath, spiral, summer 
crimp) — Plants may be sickly and stunted with discolored, stubby roots. Roots 
may show small, knotlike galls (Root-knot) . Control: Soak gladiolus corms 4 
hours in hot water (110° F.) plus 0.5 per cent formalin, or plant disease-free, 
high-quality corms in clean or sterilized soil. Drenching over the row using Nema- 
gon or Fumazone has also proved beneficial. 

9. Bulb Nematode (gladiolus, tigridia) — See (38) Bulb Nematode under General 
Diseases. 

10. Blind Buds (crocus) —Flower buds do not grow, but dry up or rot. Control: 
Water during dry periods. Avoid excessive heat after harvest and in storage. 

ll.Sraw* (gladiolus) —Rare. Elongated, black, powdery blisters or stripes in leaves, 
stems, and corms. Seedlings may shred and die early. Control: Same as for Corm 
Rots (above) . Destroy infected plants when first found. Soak corms as for Root- 
feeding Nematodes (above) . 

12. Chlorosis — Plants a sickly yellowish-green, yellow, or ivory color. Plants often 
stunted. Control: Have the soil tested. It should be near neutral. Spray plants 
with iron sulfate (1 teaspoon per gallon) . May apply with regular pest sprays 
when first noticed. Repeat as necessary. 

GLEDITSIA - See Honeylocust 

GLOBE - AMARANTH - See Cockscomb 

GLOBE ARTICHOKE - See Lettuce 

GLOBEFLOWER — See Anemone 

GLOBEMALLOW - See Hollyhock 

GLOBETHISTLE-See Chrysanthemum 

GLOBE LILY, GLOBE - TULIP - See Mariposa Lily 

GLORYBOWER - See Lantana 

GLORY - OF - THE - SNOW - See Tulip 

GLORYVINE -See Grape 



236 GLOWING GOLD 

GLOWING GOLD -See Pea 

GLOXINIA - See African - violet 

GOATSBEARD - See Rose 

GODETIA — See Fuchsia 

GOLDDUST-See Cabbage 

GOLDDUST - TREE - See Aucuba 

GOLDEN - ASTER — See Chrysanthemum 

GOLDENBELLS - See Forsythia 

GOLDENCHAfN, BEANTREE, SCOTCH LABURNUM (Laburnum) 

1. Leaf Spots — Round to irregular, light gray, grayish-brown, or brown spots on the 
leaves. Black dots or mold growth may dot the center of older spots. Control: If 
serious enough, apply zineb, maneb, or fixed copper sprays at 10- to 14-day in- 
tervals during rainy weather. 

2. Twig Blight — In wet springs, brown areas may develop on the twigs which cause 
the leaves beyond to be blighted. Control: Prune out and burn infected twigs. 
Spray as for Leaf Spots (above) . 

3. Mosaic, Infectious Variegation — Leaves mottled light and dark green. Often 
brightly variegated. Leaf veins may be yellow and stand out prominently. Growth 
of tree is apparently normal. Control: Spray or dust with malathion or lindane 
to control aphids which probably transmit the virus. Propagate only from mosaic- 
free plants. 

4. Root Rot — See under Apple, and (34) Root Rot under General Diseases. 

5. Root-knot — See (37) Root-knot under General Diseases. 

GOLDENEGGS — See Evening - primrose 

GOLDEN ELDER -See Snowberry 

GOLDENGLOW — See Chrysanthemum 

GOLDENLARCH - See Larch 

GOLDEN MARGUERITE -See Chrysanthemum 

GOLDEN - PEA - See Pea 

GOLDENRAIN-TREE (Koelreuteria) 

1. Coral Spot, Twig Canker — Coral-red cankers on twigs. Affected parts wither and 
die back. Control: Prune out and burn blighted parts. Keep trees vigorous by fer- 
tilizing and watering during dry periods. 

2. Verticillium Wilt — See under Maple, and (15B) Verticillium Wilt under Gen- 
eral Diseases. 

3. Leaf Spot — Small, tan to gray spots on the leaves. Control: None necessary. 

GOLDEN ROSE OF CHINA -See Rose 

GOLDEN - SHOWER - See Honeylocust 

GOLDENTUFT-See Cabbage 



GRAPE 237 

GOLDEN -WAVE —See Chrysanthemum 

GOLDFLOWER - See St. - Johns - wort 

GOLDTHREAD -See Delphinium 

GOMPHRENA - See Cockscomb 

GOOSEBERRY - See Currant 

GORDONIA — See Franklin - tree 

GOURDS — See Cucumber 

GRAMATOPHYLLUM - See Orchids 

GRAPE [ BIRD, CALIFORNIA, CANYON, FOX, FROST or RIVERBANK, 
EUROPEAN WINE, MUSCADINE, POSSUM, SAND, SUMMER or PIGEON, 

SWEET WINTER, and WINTER], GLORYVINE (Vitus); PEPPERVINE, 
MONKSHOOD -VINE, TURQUOISE or PORCELAIN BERRY (Ampelopsis); 
MARINE - IVY, GRAPE IVY, KANGAROO VINE (Cissus); IVY [ BOSTON, 
ENGLEMANN], VIRGINIA - CREEPER or WOODBINE, PLUME HYACINTH 

(Parffienoc/ssusJ 

1. Black Rot, Leaf Spot — Widespread. Small, more or less circular to angular, red- 
dish-brown spots on the leaves. Spots usually have dark brown margins and black 
specks in the centers. Tan-colored spots on grapes which become sunken and sur- 
rounded with a dark ring, giving a "bird's-eye" effect. The rot later turns brownish- 
black and enlarges. The berry rots and usually turns into a hard, shriveled, 
wrinkled, black mummy. Such fruits drop early. Several or all of the berries in a 
cluster may become infected (Figure 122) . Blossoms are blasted. Control: Prune 
and retie grape vines annually. Burn prunings. Space plants. Keep down weeds. 
In humid areas, apply captan, zineb, ferbam, thiram, or ziram following the grape 
spray schedule in the Appendix (Table 10) . Check with your county agent or ex- 
tension plant pathologist regarding timing of sprays for your area. Resistant grape 
varieties: Beta, Campbell Early, Champion, Cimarron, Clinton, Delaware, Dia- 
mond, Dracut Amber, Eaton, Elvira, Everglades, Lucile, Lutie, Missouri Riesling, 
Moore Early, Norton, Steuben, Tarheel, Topsail, and Worden. Check with your 
county agent or extension horticulturist regarding the adaptability of these varieties 
to your area. Cultivate in early spring to cover old fruit mummies, leaves, and other 
plant debris. 

2. Downy Mildew — Widespread. Greenish-yellow blotches on the upper leaf surface, 
which later turn reddish-brown. A dense, white, downy mold grows on the corre- 
sponding underleaf surface. Fruits, shoots, and tendrils are also attacked. Affected 
leaves and fruit may drop early. Flower clusters and young berry clusters may 
be killed. Shoot growth is stunted. See Figure 20A under General Diseases. Control: 
Same cultural practices as for Black Rot (above) . Resistant grapes: Clinton, Con- 
cord, and Lutie. Where downy mildew is a problem apply fixed copper, zineb, or 
possibly maneb following the grape spray schedule in the Appendix (Table 10) . 
Cover underleaf surface thoroughly. Start when mildew is first seen. Repeat at 
about 2-week intervals. Collect and burn fallen leaves. 

3. 2,4-D Injury — Cosmopolitan. Leaves, tendrils, and young shoots are misshapen. 
Leaves have many sawtooth edges and close yellow veins. May appear narrow, fan- 
shaped, and stiff (Figure 123) . Fruits ripen unevenly, if at all. Symptoms likely 1 
to 3 weeks after exposure to fumes or spray drift (up to a mile or more) . Control: 
Use only the amine form of 2,4-D, at low pressure, near grape, tomato, and other 
garden plantings. Apply to lawns in the fall. Apply only when air movement is 



238 GRAPE 





Fig. 123. 2,4-D injury of grape. 
State University photo) 



(Iowa 



Fig. 122. Black rot of grape. 



away from grapes and other susceptible plantings. Use a separate sprayer for apply- 
ing weed killers. 

4. Grape Fruit Rots, Fly Speck — Widespread in rainy weather. Ripening fruits rot. 
May be covered with gray, black, bluish-green, green, or pink mold growth. Con- 
trol: Handle fruit carefully. Store fruit as cool and dry as practical. Prune and re- 
tie grape vines annually. Destroy rotting fruit. Spray as for Downy Mildew (above) . 
Apply captan alone just before harvest. 

5. Powdery Mildew — General, especially from midsummer on. Indistinct or thin, 
powdery, flourlike patches on leaves, shoots (canes) , tendrils, blossoms, and young 
fruit which may later turn brown or black. If severe, may cause stunting, yellowing, 
and withering. Berries may be dwarfed, distorted, russeted, and cracked. Such 
fruit may fail to ripen or "shell off" the vine before harvest. Mildew tends to build 
up following extended use of captan sprays. Control: Spray with fixed copper as 
for Downy Mildew. If serious enough, add Karathane to 2 consecutive sprays. Keep 
down weeds. Same cultural practices as for Black Rot (above) . Resistant or toler- 
ant grapes: Clinton, Delaware, Dutchess, Early Niabell, Elvira, Ives, Niabell, and 
Royalty. 

6. Grape Dead Arm, Fruit Rot — Widespread. Locally severe in certain areas. Young 



GRAPE 239 

shoots, trunks, and branches may be weakened and killed by perennial, reddish- 
brown to purplish-black, elongated cankers. Cankers enlarge (often become ir- 
regular, black, and crusty) , and girdle the trunk or "arm." Portion beyond dies. 
Leaves on cankered canes are often dwarfed, yellowish, rolled, tattered and 
"crimped," especially along the edges. Such leaves usually drop early. Leaves which 
appear late in the season are stunted but otherwise appear normal. Suckers often 
form at the base of killed spurs giving vines a bushy appearance. Fruit may rot. 
Control: Annually prune out and burn all dead and cankered (blighted) wood at 
least 6 inches below any sign of disease. Disinfect between cuts, in diseased vine- 
yards, by dipping shears in 70 per cent denatured alcohol. Follow the spray pro- 
gram as for Black Rot and Downy Mildew (both above) . Where common, apply a 
captan spray when new shoots are i/ 2 to 1 inch long. 

7 '. Anthracnose , Bird's Eye Fruit Rot, Leaf Scab — Widespread on grape. Small, 
sunken, light-colored spots with dark margins. Found on leaves, young shoots, 
tendrils, fruit, and canes. Canes may be girdled, causing dwarfing. Leaf spots may 
drop out leaving the leaves ragged and distorted. Control: Same as for Black Rot 
and Downy Mildew (both above) or apply thiram or ziram: (1) as the buds swell, 
(2) as buds break open, and (3) when new shoots are 7 to 9 inches long. Resistant 
grapes: Beacon, Concord, Delaware, Everglades, Fredonia, Herbemont, Lutie, 
Moore Early, Niagara, and President. 

S. Crown Gall — Widespread. See under Apple, and (30) Crown Gall under General 
Diseases. 

9. Root Rots — Plants decline in vigor, gradually die. Foliage is sparse and often 
yellowish. Fruit production declines sharply. Canes are winter-killed. Roots die 
back. Often associated with root-feeding nematodes. Control: See under Apple. 
Rootstocks vary in resistance. 

10. Wood Rots — Plants gradually decline in vigor. Shoots may die back. Leaves may 
be yellowish or bronzed and scorched, puckered, and distorted. Often drop early. 
Fruit shrivel and dry up. Trunks and branches have soft, spongy, internal decay. 
Older vines are most severely infected. Control: Avoid wounding vines when culti- 
vating or mowing. Follow the spray program as for Downy Mildew and Black Rot 

(both above) . Prune and retie vines annually. Prune affected vines back to the 
ground. 

11. Root-knot — Southern states. See (37) Root-knot under General Diseases. Root- 
knot resistant grape rootstocks are available. Check with your local nurseryman or 
extension plant pathologist. Nurserymen disinfest dormant, 1 -year-old grape roof- 
ings by soaking in hot water (122° F. for 10 minutes; 125° F. for 5 minutes; or 
127° F. for 3 minutes) . Plant in clean or fumigated soil (pages 437-44) , where feas- 
ible. 

12. Boron Deficiency — Symptoms variable. Leaves develop enlarging, yellowish, then 
reddish, dead areas between the leaf veins or along the margins. Leaves often 
dwarfed, rolled, and distorted. Fall early. Growth may be stunted, bushy, and dis- 
torted. Fruit is tough and tasteless. Control: Have the soil tested and follow the 
recommendations. Apply borax in late winter and repeat once or twice more 
before bloom. 

13. Zinc Deficiency, Little Leaf — See under Walnut. Control: Swab fresh pruning 
wounds of spur-pruned vines within 3 hours after pruning during the dormant 
period. Use 1 to 2 pounds of zinc sulfate (23 per cent metallic zinc) in a gallon of 
water. When the grape shoots are 12 to 15 inches long apply a thorough spray to 
the lower leaf surface and young flower clusters using 1 ounce of zinc sulfate and 
1/2 ounce of spray lime in a gallon of water. 



240 GRAPEFRUIT 

14. Dieback, Canker, Wilt, Cane or Shoot Blight — Stems or canes are cankered. Foli- 
age wilts and dies back. Control: Prune and burn all infected branches. Spray as 
for Downy Mildew (above) . 

15. Pierce's Disease of Grape — Primarily southern states. Symptoms very variable de- 
pending on the variety, age, and locality. Vines decline in vigor. Die in several 
months to 4 to 5 years. Most varieties are slow to leaf out in the spring. Shoots 
remain dwarfed; tend to die back from the tips. Affected leaves usually drop early, 
starting at the base of the shoots. In the fall, leaf margins and areas between the 
leaf veins show more and more scalding and browning. Control: If you are sus- 
picious, check with your county agent, a local grower, or an extension plant path- 
ologist. Plant only virus-free plants. Destroying infected vines and spraying to 
control leafhoppers which transmit the virus have not been satisfactory. Keep down 
weeds. Grape species in the Gulf states are resistant. Resistant or tolerant grapes: 
Champanel, Herbemont, Lake Emerald, and Lenoir. 

16. Fanleaf, Infectious Degeneration (grape) —Leaves and new growth severely 
stunted. Secondary shoots develop abnormally with 2 or 3 buds forming double 
or treble nodes. Leaves come out at acute angle with the stem. Leaf margins more 
deeply cut than normal. Resemble a half-closed fan. Tissues are somewhat puck- 
ered and folded. Symptoms tend to disappear during the season. Fruit production 
is sharply decreased. Vine gradually becomes dwarfed. Symptoms somewhat similar 
to 2,4-D injury. Transmitted by the dagger nematode (Xiphinema) and possibly 
others, as well as by grafting. Control: Destroy infected vines when first found. 
Plant virus-free stock in fumigated soil (pages 440-44) . 

17. Leafroll of Grape (White Emperor Disease) — A virus disease, primarily in Cali- 
fornia, which is easily confused with potassium deficiency. Plants may be severely 
stunted. Leaves are darker than normal, turning a bronze or reddish color along 
the veins and yellow between the veins. Leaves turn color early with the lower 
leaves appearing scorched and rolled downward and inward. Fruit yield and 
quality are greatly reduced. Normally red fruit remains greenish-white, greenish- 
yellow, or pink. The virus interferes with the movement of potassium within the 
vine. Control: Destroy infected plants. Replant with virus-free stock. Keep the 
potassium level up, based on a soil test. 

18. Yellow Mosaic (grape) —Symptoms variable. Leaves variously mottled and yel- 
lowed. Blossoms drop early. Control: Same as for Fanleaf (above) . 

19. Other Leaf Spots or Blotches, Spot Anthracnose — Widespread. Spots of various 
sizes, shapes, and colors on the leaves. Control: Same as for Black Rot (above) . 

20. Other Root-feeding Nematodes (citrus, dagger, pin, ring, root-lesion or meadow, 
spiral, sting, stylet or stunt, stubby-root) — Plants may be sickly, gradually decline. 
Control: Same as for Root-knot (above) . 

21. Thread Blight (peppervine, Virginia-creeper) —Southeastern states. See under 
Walnut. 

22. Rust (grape) — Southeastern states. See (8) Rust under General Diseases. Control: 
Same as for Black Rot and Downy Mildew (above) . 

23. Chlorosis — Mineral deficiency in alkaline soil. See under Maple. 

GRAPEFRUIT -See Citrus 
GRAPE - HYACINTH - See Tulip 

GRAPE IVY -See Grape 

GRASS PINK -See Carnation 

GREAT LAUREL -See Rhododendron 



HAMAMELIS 241 

GREEK VALERIAN - See Phlox 

GREVILLEA - See Silk -oak 

GROMWELL — See Mertensict 

GROUNDCHERRY - See Tomato 

GROUND -IVY -See Salvia 

GROUND - MYRTLE - See Vinca 

GROUND -PINK -See Phlox 

GROUNDSEL — See Chrysanthemum 

GUAVA-See Myrtle 

GUERNSEY - LILY - See Daffodil 

GUINEA BEAN -See Cucumber 

GUINEA - HEN FLOWER - See Tulip 

GYMNOCLADUS - See Honeylocust 

GYPSOPHILA - See Carnation 

HACKBERRY [CHINESE, COMMON, SOUTHERN or SUGARBERRY] 

(Celtis) 

1. Witches' -broom — Widespread, especially in central states. Unsightly, tight clusters 
of dwarfed twigs evident in the dormant season (Figure 124) . Several hundred 
witches'-broom galls may be found on a single tree. Twigs may die back. Trees 
vary greatly in susceptibility. Control: Plant somewhat resistant types, e.g., Chinese 
and Southern. Cut and burn "brooms" back to healthy wood. A dormant lime- 
sulfur spray may be beneficial. 

2. Powdery Mildews — Widespread. Powdery, white mold growth on both leaf surfaces. 
Control: If practical, apply a dormant spray of lime-sulfur. When mildew appears 
apply one or two sprays of Karathane or sulfur. 

3. Wood Rots — Cosmopolitan. See under Birch, and (23) Wood Rot under General 
Diseases. 

4. Root Rots — See under Apple, and (34) Root Rot under General Diseases. 

5. Leaf Spots, Leaf Blight — General. See under Maple. 

6. Winter Injury — See under Elm. 

7. Downy Mildew — See (6) Downy Mildew under General Diseases. 

8. Mosaic — See under Elm. 

9. Mistletoe — See (39) Mistletoe under General Diseases. 

10. Felt Fungus — Southern states on neglected trees infested with scale insects. Dark, 
sometimes ringed, feltlike growth over scales. Control: Spray with DDT and mala- 
thion to control "crawler" stage of scales. Check with your extension entomologist 
regarding timing of sprays. 

11. Thread Blight — Southeastern states. See under Walnut. 

HALESIA - See Silverbell 
HAMAMELIS - See Witch - hazel 



242 HARDHACK 




Fig. 124. Witches'-broom of hackberry. 
(Iowa State University photo) 



HARDHACK -See Spirea 

HARDY AMARYLLIS - See Daffodil 

HARDY ORANGE -See Citrus 

HAREBELL - See Bellf lower 

HAWKSBEARD - See Chrysanthemum 

HAWORTHIA - See Aloe 

HAWTHORN -See Apple 

HAZELNUT -See Birch 

HEAL -ALL -See Salvia 

HEARTS AND HONEY VINE- See Morning -glory 



HELIANTHUS 243 

HEATH [CORNISH, CROSS - LEAVED, DARLEY, FRINGED, MOOR, SCOTCH, 

SPRING, TWISTED ] (Erica); WINTERGREEN (EASTERN or WESTERN) or 

CHECKERBERRY, TEABERRY, SHALLON or SALAL (Gaultheria); HEATHER 

(Calluna); TRAILING - ARBUTUS [ AMERICAN or MAYFLOWER, JAPANESE ] 

(Epigaea) 

1. Wilt, Root and Collar Rot, Stem Rot — Plants wilt, wither, and die from a rotting 
of the stem, crown, and roots. Leaves have a grayish appearance before wilting. 
Control: Plant disease-free plants in clean or sterilized soil (pages 437-44) , which 
is light and well-drained. Avoid overwatering. Grow resistant varieties (e.g., Erica 
persoluta). 

2. Powdery Mildew, Twist — May be serious on salal. Youngest leaves redden, later 
turn yellow to brown and drop early. Infected leaves are covered with whitish-gray 
mold patches especially on the lower leaf surface. Plants are dwarfed, bushy, and 
twisted. May die back. Blooming is reduced. Control: Dust or spray several times 
at weekly intervals using Karathane or sulfur. Space plants. 

3. Chlorosis, "Yellows" — Plants lack vigor. New growth is stunted and pale yellow 
to whitish. Branches or entire plants die back. Control: Plant in light, well-drained 
soil which is quite acid. Spray plants monthly with iron sulfate. Avoid use of lime 
in any form. 

4. Rust (heath) — Orange, powdery pustules on leaves. Infected leaves later turn 
yellow, wither, and drop early. Control: Spray or dust several times in early spring. 
Use zineb, maneb, or dichlone. 

5. Verticillium Wilt of Heath — One or all branches may turn yellowish-green, wilt, 
and die. Disease usually progresses up the plant. Control: Grow disease-free, resist- 
ant varieties in soil free of the causal fungus. Or plant in sterilized soil. 

6. Damping-off, Cutting Rot — Seedlings wilt and collapse. Cuttings rot at the base. 
Control: Use clean or sterilized soil for starting seed or cuttings. Avoid overwater- 
ing. Apply a drench of thiram or zineb (1 tablespoon per gallon) if disease strikes. 
Repeat 5 to 7 days later. 

7. Sooty Mold, Black Mildew — Black patches of mold on foliage following insect 
attacks. Control: Apply malathion to control insects. 

8. Leaf Spots, Fruit Spot, Spot Anthracnose — General on gaultheria. Spots of various 
colors, sizes, and shapes on leaves and fruit. If severe, leaves may wither and fall 
early. Control: Same as for Rust (above) . 

9. Gray-mold Blight — See (5) Botrytis Blight under General Diseases. 

10. Red Leaf Gall (gaultheria) — Northern states. Small, red galls on the foliage. 
Control: Pick off and burn affected parts. 

HEATHER -See Heath 

HEAVENLY BAMBOO - See Nandina 

HEBE — See Speedwell 

HEDERA-See Ivy 

HEDGENETTLE - See Salvia 

HEDGETHORN - See Oleander 

HELENIUM - See Chrysanthemum 

HELIANTHEMUM - See Sunrose 

HELIANTHUS — See Chrysanthemum and Lettuce 



244 HELICHRYSUM 

HELICHRYSUM, HELIOPSIS - See Chrysanthemum 

HELIOTROPE (Heliotropium) — See Mertensia 

HELLEBORUS-See Delphinium 

HELXINE-See Babytears Vine 

HEMEROCALLIS, DAYLILY (Hemerocallis) 

1. Leaf Spots — Small, more or less round, tan to gray or black spots on the leaves. 
One leaf spot has a fairly broad, dark red border. Control: Collect and burn in- 
fected leaves as they appear. Cut and burn tops late in the fall. 

2. Root-knot — Gall-like growths on the roots or discolored spots within the fleshy 
roots. Control: Plant disease-free stock in clean or fumigated soil (pages 437-44) . 

3. Root Rots — See under Geranium, and (34) Root Rot under General Diseases. 
May be associated with nematodes (e.g., root-knot, spiral) . 

4. Gray-mold Blight — See (5) Botrytis Blight under General Diseases. 

5. Russet Spot — Greenish-yellow spots develop on the leaves. Spots later enlarge and 
turn an orange-brown color. Tips or even entire leaves may wither and die. Varie- 
ties differ greatly in susceptibility. Control: Grow plants in partial shade. 

6. Winter or Frost Injury — Plants start slowly in the spring with a few yellowish, 
malformed leaves and little vigor. Most common with evergreen types. Crowns 
may decay. Shoots are often stunted or spindling. Plants may or may not recover. 
Frost injury due to late spring freezes appears as brown or tattered leaf tips 
followed later by normal development and flowering. Control: A mulch will help 
delay early growth until danger of frost is past. 

7. Daylily Blight — One or more flower stems suddenly wither and die. Part or all of 
the foliage turns yellowish-brown and dies, usually after a flower stem has blighted. 
Roots are decayed. Plants usually recover in the same or the following season. 
Control: Unknown. 

HEMLOCK -See Pine 

HEN -AND -CHICKENS -See Sedum 

HEPATICA — See Anemone 

HERB ROBERT -See Cranesbill 

HERCULES- CLUB — See Acanthopanax and Hoptree 

HERONSBILL-See Cranesbill 

HESPERIS-See Cabbage 

HEUCHERA-See Hydrangea 

HIBA ARBORVITAE - See Juniper 

HIBISCUS -See Hollyhock 

HICKORY -See Walnut 

HIGHBUSH CRANBERRY - See Viburnum 

HINOKI CYPRESS -See Juniper 



HOLLY 245 

HOLLY [AMERICAN or CHRISTMAS, CHINESE, ENGLISH or EUROPEAN 

(HEDGEHOG, SILVER - EDGE), JAPANESE, LUSTER LEAF, MOUNTAIN], 

DAHOON, INKBERRY, POSSUMHAW, WINTERBERRY (BLACK - ALDER) or 

NORTHERN HOLLY, JAPANESE WINTERBERRY, YAUPON (Ilex); 

MOUNTAIN HOLLY (Nemopanthus) 

1. Leaf Spots, Tar Spot, Leaf and Twig Blight, Spot Anthracnose — Spots of various 
colors, sizes, and shapes on the leaves. Most spots are yellow, gray, to reddish-brown 
or black in color. Sometimes with a yellow or purplish margin. Spots may drop 
out leaving shot-holes. Young twigs may die back. May be serious in the nursery. 
Control: Pick off and burn spotted leaves where practical. Fertilize and water to 
maintain good tree vigor. Check with your nurseryman or extension horticulturist. 
If serious, spray with zineb, ferbam, or dichlone at 2-week intervals starting in late 
spring. Repeat sprays during late summer or early fall wet periods. Space plants. 
Plant where air circulation is fair to good. Removal of the lower branches plus 
collecting and burning the fallen leaves is often beneficial. 

2. Spine Spot — Small, grayish-brown spots, usually surrounded with a purplish border, 
appear on the upper leaf surface in late winter or early spring. Spots are caused by 
wounding of spines from nearby leaves during high winds. Control: Plant trees 
in a sheltered location or erect canvas or burlap barriers to prevent wind-whipping 
of the leaves. 

3. Leaf Scorch — Leaves, especially near the margins, are a scorched brown or purplish 
color in late winter or early spring. Occurs in wind-swept areas or when the sun 
shines brightly on ice-coated leaves. Control: Same as for Spine Spot (above) . 

4. Powdery Mildews — Mostly southern states. Grayish-white mold blotches on the foli- 
age. Control: Where serious enough, spray with Karathane. 

5. Twig Blights, Cankers, Dieback — Light brown to black, sunken cankers develop 
on the twigs and branches. Affected parts die back when girdled. Control: Prune 
out dead or cankered twigs and branches. Spray as for Leaf Spots (above) during 
cool, rainy, spring and fall weather. 

6. Sooty Molds, Black Mildews — Primarily Gulf states. Black mold patches on foliage 
following attacks by insects. Control: Control whiteflies, scales, and other insects by 
using malathion sprays. 

7. Rust — American holly is attacked in southern states. See (8) Rust under General 
Diseases. 

8. Wood Rots — See under Birch, and (23) Wood Rot under General Diseases. 

9. Root Rots — See under Apple, and (34) Root Rot under General Diseases. May be 
associated with nematodes (e.g., burrowing, dagger, lance, pin, ring, root-knot, 
root-lesion, sheath, spiral, sting, stubby-root, stylet or stunt) . 

10. Chlorosis— Occurs in alkaline soils. See under Maple. 

11. Leaf Rot or Drop of Cuttings (American and English holly) — Lower leaves decay 
and drop off when cuttings are in the rooting medium. Control: Stick cuttings in 
clean, fresh sand or sterilize old sand with heat or chemicals. Drench cutting bench 
with Terra clor 75 per cent (1 tablespoon per gallon) . Use 1 pint per square foot. 
Take cuttings only from branches that do not touch the ground. 

12. Thread Blights — Southeastern states. See under Walnut. Control: Spray as for 
Leaf Spots (above) . 

13. Felt Fungus — Southern states. Smooth, shiny, chocolate-brown to almost black 
growth on the bark. See under Hackberry. 



246 



HOLLYGRAPE 



HOLLYGRAPE - See Barberry 

HOLLYHOCK [ ANTWERP, COMMON ] (Althaea); ABUTILON, FLOWERING - 

MAPLE (Abutilon); ANODA; POPPY -MALLOW (Callirhoe); ROSELLE, 

ROSEMALLOW, FLOWER - OF - AN - HOUR, CHINESE HIBISCUS, COTTON - 

ROSE, CONFEDERATE - ROSE, ROSE - OF - SHARON or SHRUB - ALTHAEA, 

OKRA (Hibiscus); TREEMALLOW (Lavatera); MALLOW [ HIGH, MUSK ] 

(Malva); FALSE - MALLOW, BUSH - MALLOW, (Malvastrum); SIDA; 

CHECKERMALLOW (Sidalcea); GLOBEMALLOW (Sphaeralcea) 

I. Rusts — General and destructive. Small, orange-yellow spots on the leaves, bracts, 
and stems. Pustules may later become powdery and reddish-brown to chocolate- 
brown in color. Mostly on underleaf surface. If severe, leaves may turn yellow, 
wither, and die early. See Figure 125. Control: Where practical, collect and burn 
all tops in the fall. Pick off and burn the first infected leaves as they appear in early 



i UPPER SIDE 




Fig. 125. Hollyhock rust. 



spring. Destroy round leaf mallow or cheeseweed growing nearby. These plants 
may also be attacked, as are various wild grasses such as Muhlenbergia, Sporobolus, 
and Stipa. Keep down weeds. Plant only seed from healthy plants. Hollyhock 
varieties differ in resistance. Apply zineb, maneb, ferbam, dichlone, or sulfur at 
weekly intervals. Start as soon as growth begins. Repeat applications in late summer. 

2. Anthracnose , Dieback, Seedling Blight — May be serious in hot, humid weather. 
Black blotches on the stem, petioles, and even the roots. Angular, grayish to black 
spots on the leaves with a dark margin, which may later drop out, leaving 'shot- 
holes.' Shoot tips may die back. Control: Same as for Rusts (above) . 

3. Leaf Spots, Stem Canker, Pod Spot, Blossom Blight — Spots of various colors, sizes, 
and shapes on the leaves. Some spots may drop out. If severe, leaves may wilt, 
roll, wither, and drop early. Similar spots may occur on the stems, pods, and 
flowers. May be covered with dense mold growth or sprinkled with black dots. 



HOLODISCUS 247 

Control: Same as for Rusts (above) . Plant in well-drained soil. Rotate. Keep 
plants growing vigorously. 

4. Stem Canker, Stem or Crown Rots, Southern Blight — Girdling cankers on the stems 
near the ground line. Cankers often water-soaked and dark green at first. Later 
become covered with a cottony mold or become white, tan, or yellowish-brown in 
color. Control: Dig up and burn infected plants and 6 inches of surrounding soil. 
If practical, sterilize infected soil (pages 437-44) or treat with Terraclor (PCNB) 
dust or spray before planting. Rotate. Plant in well-drained soil. Avoid over- 
watering, shading, and crowding plants. 

5. Root-knot — Primarily southern states. Hollyhock is very susceptible. See (37) Root- 
knot under General Diseases. 

6. Powdery Mildews — Powdery white growth on leaves. Control: If serious enough, 
spray or dust at 7- to 10-day intervals using sulfur or Kara thane. 

7. Crown Gall and Hairy Root — See (30) Crown Gall under General Diseases. 

8. Bacterial Wilt — Southern states. See under Tomato, and (15C) Bacterial Wilt 
under General Diseases. 

9. Verticillium Wilt (abutilon, okra, poppy-mallow) — Widespread. See under Bell- 
flower, and (15B) Verticillium Wilt under General Diseases. 

10. Fusarium Wilt (okra) —Serious in commercial okra-growing areas. Plants are pro- 
gressively stunted and yellowed. Gradually die. Leaves wilt and roll. Dark streaks 
occur inside infected stems and roots. May be associated with nematodes (see be- 
low) . Control: If destructive, plant in wilt-free soil or practice a 6-year rotation 
or longer. 

11. Mosaic, Infectious Variegation (abutilon, Chinese hibiscus, lavatera, hollyhock, 
mallow, sida, sidalcea, treemallow) — Variegated forms of abutilon and treemallow 
are infected, often increasing the ornamental value. Leaves are mottled a bright 
yellow and green. Leaf veins may be yellow. Propagated by grafting and occasion- 
ally by seed of certain species. A branch or plant may apparently outgrow the 
virus and appear normal. 

12. Seed Rot, Damping-off — Seeds rot. Stand is poor. Seedlings may wilt and collapse. 
Control: Plant in warm, well-drained soil. Treat seed with thiram, captan, chlor- 
anil, or dichlone. Avoid overwatering. 

13. Root Rots — See (34) Root Rot under General Diseases. May be associated with 
nematodes (e.g., burrowing, dagger, lance, pin, reniform, ring, root-lesion or 
meadow, spiral, stem, sting, stubby-root, stylet or stunt) . 

14. Curly-top (mallow, okra) —See (19) Curly-top under General Diseases. 

15. Spotted Wilt and Yellows (mallow, okra) -See (17) Spotted Wilt and (18) Yel- 
lows under General Diseases. 

16. Web Blight, Thread Blight — Southeastern states. See under Bean and Walnut. 

17. Twig Blight (hibiscus) —See under Maple. 

18. Strapleaf, Molybdenum Deficiency (hibiscus) —Florida. See under Cabbage. 

HOLLY - OSMANTHUS - See Osmanthus 
HOLODISCUS, OCEANSPRAY, ROCKSPIREA (Holodiscus) 

1. Leaf Spots, Leaf Blight — Western states. Spots of various sizes, shapes, and colors 
on the leaves. Control: If serious enough, apply several sprays at 10- to 14-day in- 
tervals during wet periods. Use zineb, maneb, or fixed copper. 

2. Powdery Mildew — Western states. Grayish-white, mold patches on the foliage. 
Control: Apply 2 or 3 sprays of sulfur or Karathane, 10 days apart. 



248 HOMALOMENA 

3. Twig Canker, Dieback, Coral Spot — Pacific Northwest. Twigs die back due to 
girdling cankers. Cankered areas may be covered with small, coral-pink fruiting 
bodies of the causal fungus. Control: Prune out and burn cankered twigs. Keep 
trees growing vigorously. Spraying as for Leaf Spots (above) may be beneficial. 

4. Witches' -broom — Pacific Northwest. New lateral branches are very slender and 
wirelike with small, crowded leaves. In later years, several to many laterals arise 
from the same area on the stem (witches'-broom) and are much branched. Non- 
shaded leaves turn a bronzy-red color in early summer. Affected plants do not 
bloom. Control: Remove and burn infected plants. Protect healthy plants by con- 
trolling aphids, which transmit the virus. 

5. Fire Blight — See under Apple. 

HOMALOMENA - See Calla 

HONESTY -See Cabbage 

HONEYDEW MELON -See Cucumber 

HONEYLOCUST (many horticultural varieties) (Gleditsia); ACACIA 

[CULTIVATED, MESCAT, PRAIRIE, SWEET], CATCLAW [ LONG - FLOWERED, 

ROUND - FLOWERED, TEXAS] (Acacia); SILKTREE, "MIMOSA," LEBBEK 

(Alhizzia); CAESALPINIA; PEA -TREE, PEA -SHRUB (Caragana); SENNA, 

GOLDEN - SHOWER (Cassia); REDBUD [ CHINESE, COMMON, WESTERN, 

WHITE -FLOWERED], JUDAS-TREE (Cercis;,- YELLOWWOOD, AMERICAN 

YELLOWWOOD (Cladrastis); BLADDER - SENNA (Colutea); ERYTHRINA, RED - 

CARDINAL, CORAL -TREE, CORALBEAN (Erythrina); KENTUCKY COFFEETREE 

(Gymnoc/ac/us;; LEADTREE (Leucaena); PARKINSONIA, JERUSALEM - THORN 

(Parkinsonian POINCIANA; LOCUST [ BLACK or FALSE - ACACIA, BRISTLY 

OR MOSSY, CLAMMY, KELSEY, NEW MEXICO] (Robinia); SOPHORA 

[MESCALBEAN or FRIJOLITO, VETCHLEAF], JAPANESE PAGODA-TREE 

or CHINESE SCHOLARTREE, SILKY SOPHORA (Sophora); WISTERIA 

[ AMERICAN, CHINESE, JAPANESE ] (Wisteria) 

I.Wood or Heart Rots — General. See under Birch, and (23) Wood Rot under 
General Diseases. Wood rot fungi frequently follow borers and other insects. 

2. Twig Blights, Branch Cankers, Dieback, Wilt — Discolored, slightly sunken cank- 
ers girdle the twigs and branches causing the parts beyond to wither and die. 
Small coral-pink to black "pimples" may be evident on affected wood. Trees may 
die back. Often follows freezing injury, borers, and bark wounds. Control: Severely 
cankered branches should be pruned out and burned. Keep trees growing vigor- 
ously by fertilizing and watering during summer dry periods. Grow varieties and 
species adapted and recommended for your area. Check with your nurseryman 
or extension horticulturist. Control borers with DDT or dieldrin sprays. Avoid 
bark injuries. 

3. Powdery Mildews — Widespread. Powdery, grayish-white mold on the leaves and 
young shoots. If severe, leaves may turn yellow, wither, and fall. Control: Where 
feasible, apply sulfur or Kara thane twice 10 days apart. 

4. Root and Crown Rots — Trees decline in vigor. Foliage is thin and sickly. Leaves 
may turn yellow, wither, and drop early. See under Apple, and (34) Root Rot 
under General Diseases. May be associated with nematodes (e.g., burrowing, pin, 
root-knot, root-lesion, spiral, stubby-root, stylet or stunt) . 



HOPHORNBEAM 249 

5. Fusarium Wilt of "Mimosa" or Silktree — Serious in eastern and southeastern 
states. Leaves turn yellow, wilt, shrivel, and hang on the twigs. Leaves later fall 
and the branch dies. Brown streaks in the wood under the bark. Trunks may 
"bleed" extensively in the early stages of the disease. Tree dies within a year, 
branch by branch. Nematode injury to the roots speeds up wilting. Control: Cut 
down and burn infected trees. Disinfect pruning cuts with a disinfectant (e.g., 
70 per cent denatured alcohol or 1:1,000 solution of mercuric chloride) and cover 
with a tree wound dressing (page 25) . Grow wilt-resistant strains: Charlotte, 
Tyron, and U.S. No. 64. Better still, plant a different type of shade tree. Check 
with your extension horticulturist or nurseryman. 

6. Leaf Spots or Blights, Anthracnose, Tar Spot — General in wet seasons. May be 
serious in southern states. Small to large, round to irregular spots and blotches on 
the leaves. Leaves may be blighted and drop early. Control: Same as for Maple 
Anthracnose and Leaf Spots. 

7. Collar Rot, Trunk Canker — See under Dogwood. 

8. Witches' -broom, Brooming Disease (black locust, honeylocust, sophora) — East- 
ern half of the United States. New leaves are stunted with light-colored veins. 
Dense clusters or bunches (witches'-brooms) of short, spindling shoots with 
dwarfed leaves. Brooming usually occurs in late summer. Brooms tend to die 
back during the winter. Common on young sprouts following cutting of twigs, 
branches, or trunk. Witches'-brooms also form on roots. Control: Where severe, re- 
move and destroy infected trees. Trees have also appeared to recover naturally. 

9. Verticillium Wilt — See under Maple. Greenish to brown or black streaks in the 
sapwood of larger wilting or dead branches. 

10. Sunscald, Winter Injury — See under Apple. 

11. 2,4-D Injury — See under Grape and Figure 1. 

12. Crown Gall, Hairy Root — See under Apple, and (30) Crown Gall under General 
Diseases. 

13. Root-knot — See under Peach, and (37) Root-knot under General Diseases. Nurs- 
erymen soak dormant black locust trees in hot water (118° F.) for 30 minutes. 

14. Rusts (acacia, bladder-senna, caesalpinia, honeylocust, leadtree, poinciana, soph- 
ora) — Reddish-brown or black, powdery pustules on the leaves. Control: Same 
as for Leaf Spots (above) . 

15. Damping-off, Seedling Blights — Seedlings wilt and collapse. Stem at ground line 
decays. Control: Set out seedlings in clean or sterilized soil (pages 437-44) which 
is light and well-drained. See under Pine. 

16. Chlorosis — Iron or zinc deficiency in alkaline soils. See under Maple and Walnut. 

17. Mosaic (wisteria) —New leaves first show yellowish blotches with scattered green 
"islands." Older leaves are laterally twisted. Control: Do not propagate from 
virus-infected plants. 

18. Mistletoe — See (39) Mistletoe under General Diseases. 

19. Thread Blights — Southeastern states. See under Walnut. 

20. Sooty Mold (parkinsonia) — See (12) Sooty Mold under General Diseases. 

21. Felt Fungus — Southern states. See under Hackberry. 

22. Downy Mildew (redbud) — See (6) Downy Mildew under General Diseases. 

HONEYSUCKLE - See Snowberry 
HOPHORNBEAM -See Birch 



250 



HOPTREE 



HOPTREE or WAFER ASH (Ptelea); PRICKLY - ASH [ COMMON, FLATSPINE, 
LIME], HERCULES -CLUB (Zanthoxylum) 

1. Leaf Spots, Tar Spot — Not serious. Small, round to irregular spots on the leaves. 
Control: Pick off and burn spotted leaves. If serious enough, spray at 10-day inter- 
vals during rainy periods. Use zineb or maneb. Collect and burn fallen leaves in 
the autumn. 

2. Rusts — Small, yellow or yellowish-orange spots on the leaves. Alternate host is a 
wild grass (Tridens or Andropogon) . Control: Same as for Leaf Spots (above) . 

3. Twig and Stem Canker — Cankers girdle twigs causing them to die back. Control: 
Cut out cankered twigs. Spray as for Leaf Spots (above) . 

4. Wood Rot (prickly-ash) — See under Birch, and (23) Wood Rot under General 
Diseases. 

5. Mistletoe (hercules-club, prickly-ash) — See (39) Mistletoe under General Diseases. 

6. Powdery Mildew (hoptree, prickly-ash) — Widespread. Powdery, white mold on 
the leaves. Control: See under Horsechestnut. 

7. Sooty Blotch — See under Apple, and (12) Sooty Mold under General Diseases. 

8. Root Rot — See (34) Root Rot under General Diseases. 

HOREHOUND-See Salvia 

HORNBEAM -See Birch 

HORSECHESTNUT [ BAUMANN'S COMMON, DAMASK, RED, SCARLET], 
BUCKEYE [ BOTTLEBRUSH, CALIFORNIA, OHIO, RED, TEXAS, YELLOW ] 

(Aesculus) 

l.Leaf B lotch — Widespread and serious, especially on common horsechestnut and 
Ohio buckeye. Small to large, irregular, reddish-brown spots or blotches often with 



HEALTHY 




EARLY STAGE 



Fig. 126. Horsechestnut leaf blotch. 



LATE STAGE 



HOST A 251 



bright yellow borders on the leaves. Small black specks later appear in the centers 
of the spots. Infected leaves usually curl, dry, and fall prematurely. Trees often 
appear scorched by midsummer. Spots also occur on the nuts and leaf stalks. May 
closely resemble Leaf Scorch which results from drought and unfavorable growing 
conditions. See Figure 126. Control: Rake and burn leaves in the fall. If practical, 
spray two to four times, 10 to 14 days apart (or just before rainy periods) starting 
when the buds break open. Use Cyprex (dodine) , zineb, ziram, captan, or fixed 
copper. Fertilize and water weakened trees. 

2. Leaf Scorch — Margins of leaves become brown and curled in July or August. 
Scorch may spread over the entire leaflet. Most evident on the side of the tree 
exposed to wind and sun. Most prevalent in the top of the tree. Control: Prune 
susceptible trees to open them up. Water liberally during hot, dry periods. Fertilize 
to keep trees vigorous. 

3. Leaf Spots, Anthracnose — Tips of shoots may die back several inches. Spots on 
leaves are round to irregular, vary in color and size. Control: Same as for Leaf 
Blotch (above) . 

4. Powdery Mildews — General, especially in eastern and central states. Underside of 
leaves covered with white mold patches in late summer and fall. Control: If prac- 
tical, spray two or three times, 7 to 10 days apart, starting when mildew is first seen. 
Use sulfur or Karathane. 

5. Wood Rots — See under Birch, and (23) Wood Rot under General Diseases. 

6. Twig Blight, Branch and Trunk Cankers, Dieback — General. Twigs and branches 
die back. Leaves drop early. Control: See under Elm and Maple. 

7. Verticillium Wilt — See under Maple. Leaves on individual branches wilt, turn 
yellow or brown, and drop from late spring to September. New, stunted leaves may 
form later in the season. 

8. Slime Flux, Wetwood — See under Elm. 

9. Root Rot — Cosmopolitan. See under Apple, and (34) Root Rot under General 
Diseases. 

10. Yellow Leaf Blister, W 'itches' '-broom — Yellow blisters on leaves which turn a dull 
red. Witches'-brooms are formed. See under Birch. 

11. Rust — Midwest. See (8) Rust under General Diseases. 

12. Bleeding Can ker — Northeastern states. See under Beech and Maple. 

13. Mistletoe — See (39) Mistletoe under General Diseases. 

HORSEMINT-See Salvia 
HORSERADISH - See Cabbage 
HORTENSIA - See Hydrangea 
HOSTA, PLANTAINLILY (Hosta) 

1. Crown Rot, Root Rot — Plants wilt and collapse from a rot at the soil line or be- 
low. Crown may be covered with a gray or cottony mold growth. Control: Carefully 
dig out and burn infected plants and 6 inches of surrounding soil. Set out disease- 
free plants in clean or sterilized soil (pages 437-44) . A week before planting work 
Terraclor (PCNB) dust into the top 4 to 6 inches of soil following the manu- 
facturer's directions. 

2. Leaf Spots, Anthracnose — Small to large spots on the leaves and stems. Leaves may 
be disfigured. Control: Collect and burn plant debris in the fall. Spray during wet 
periods using zineb, maneb, or fixed copper. 



252 HOUNDSTONGUE 

HOUNDSTONGUE - See Mertensia 

HOUSELEEK - See Sedum 

HOUSTONIA - See Buttonbush 

HUCKLEBERRY - See Blueberry 

HUSK - TOMATO - See Tomato 

HYACINTH - See Tulip 

HYACINTH - BEAN - See Pea 

HYDRANGEA [CHINESE, CLIMBING, HILLS - OF - SNOW, HOUSE or 

HORTENSIA, OAKLEAF, PANICLE, PEEGEE, SMOOTH, SNOWHILL ] 

(Hydrangea); DECUMARIA; DEUTZIA [ FUZZY, LEMOINE, SLENDER ] 

(Deutiia); FENDLERA; CORALBELLS, ALUMROOT (HeucfieraJ; 
MITREWORT or BISHOPSCAP (Mitella); MOCKORANGE [ GOLDEN, 
GORDON, LEMOINE, STAR, SWEET, VIRGINAL, ZEYHER ] (Philadelphus); 
SAXIFRAGE (Saxifraga); FOAMFLOWER (Tiarella) 

1. Powdery Mildews (foamflower, heuchera, hydrangea, mitella, mockorange, saxi- 
frage) — General. White to grayish, powdery mold patches on the leaves, stem tips, 
and flowers. Leaves and flowers are stunted and distorted. May die early. Control: 
Apply Karathane, Acti-dione, or sulfur two or three times, a week apart. Can com- 
bine with materials to control Leaf Spots or Gray-mold Blight (both below) . In- 
doors, avoid extreme temperature changes and reduce the humidity. Varieties differ 
in resistance. 

2. Gray-mold Blight, Botrytis Blight, Bud Blight, Flower and Shoot Blight— Cosmo- 
politan on hydrangea and mockorange, especially in humid areas. Flower clusters, 
buds, and shoots turn brown and rot. Often covered with a grayish-brown mold in 
damp weather. May follow frost injury. Serious in wet seasons. Control: Indoors, 
keep water off the foliage, space plants, and keep down the humidity. Carefully 
collect and burn infected flower clusters. Spray flower buds just before opening 
using captan, maneb, or zineb. 

3. Leaf Spots, Flower Spot — General. May be serious in rainy seasons. Small- to 
medium-sized spots, round to angular or irregular, of various colors on the leaves 
and blossoms. Affected parts may sometimes be killed. Control: Same as for Gray- 
mold Blight (above) . Where practical, pick off and burn spotted leaves. Apply 
captan, maneb, zineb, thiram, ferbam, or fixed copper at 7- to 10-day intervals, 
starting when the spots are first evident. Stop when flowers start to appear. 

4. Bacterial Wilt (hydrangea) — Flowers, buds, and young leaves wilt and turn brown. 
Roots rot. Many plants may die. Most serious in hot, humid weather. Control: 
Destroy infected plant parts. 

5. Rusts (coralbells, fendlera, foamflower, hydrangea, mitella, mockorange, saxi- 
frage) — Widespread. Small, yellowish or reddish-brown, powdery pustules mostly 
on underside of leaves. Severely infected leaves may wither and die early. Alternate 
hosts: hemlocks or junipers. Control: Same as for Leaf Spots (above) . Apply zineb, 
ferbam, maneb, or dichlone. 

6. Root-knot — Deutzia is commonly attacked. See (37) Root-knot under General 
Diseases. 

7. Chlorosis (primarily hydrangea) — Leaves yellowish, plants stunted, flower color 
is poor. Common in alkaline or lime-rich soils. Control: Have the soil tested. Grow 
plants in slightly acid soil. Add an acid fertilizer such as ammonium sulfate. Water 



INDIAN CHERRY 253 

plants with a weak solution of ferrous (iron) or magnesium sulfate or a mixture 
of the two. Or spray with an iron chelate following the manufacturer's directions. 

8. Wood Rot — See under Birch, and (23) Wood Rot under General Diseases. 

9. Sooty Mold or Blotch (mockorange) —See (12) Sooty Mold under General 
Diseases. 

10. Leaf and Stem Nematodes (coralbells, hydrangea) — See (20) Leaf Nematode under 
General Diseases. 

W.Dieback, Twig Canker (hydrangea, mockorange) —Round to irregular, rough, dis- 
colored cankers on the stems. Twigs and branches are killed back. Control: Cut out 
and burn infected parts. Spray as for Leaf Spots (above) . 

12. Stem or Crown Rot (hydrangea) —Primarily an indoor problem. Stem rots, wilts, 
and collapses from a rot at the soil line which may be covered with a cottony mold 
growth. See under Cutting Rot (below) . 

13. Cutting Rot, Damping-off — Base of cuttings decay and fail to root. Seedlings wilt 
and collapse. Control: Plant in a sterile rooting medium. Avoid overwatering and 
plunging cuttings too deeply. Destroy infected cuttings. 

14. Sunscald (primarily hydrangea) — Exposed, tender leaves are "scorched" by hot 
sun, temperatures over 100° F., excessive wind, or toxic sprays. Leaf edges turn 
brown. Control: Keep plants out of direct sun and dry winds on hot days. Wrap 
trunks of young, recently transplanted trees. See under Apple and Elm. Varieties 
differ in resistance. 

15. Leaf and Stem Smut (coralbells) —See (11) Smut under General Diseases. 

16. Root Rots — See under Geranium, and (34) Root Rot under General Diseases. 
May be associated with root-feeding nematodes (e.g., dagger, pin, ring, spiral, stem, 
root-lesion or meadow) . 

17. Ringspots (hydrangea) —Symptoms variable. Leaves dull and yellowish with dark 
green to yellowish blotches, yellow or brown rings and oakleaf patterns. Plants 
dwarfed with stunted leaves. Leaves often irregular in shape, narrow, sometimes 
stiff and brittle. Flowers stunted, may open irregularly, with green and colored 
flowers in the same cluster. Control: Destroy infected plants. Take cuttings only 
from healthy plants. 

HYMENOCALUS - See Daffodil 

HYPERICUM -See St. -Johns -wort 

HYSSOP (Hyssopus) - See Salvia 

IBERIS — See Cabbage 

ICEPLANT, FIGMARIGOLD (Mesembryanthemum, Cryophytum) 

1. Root-knot — See (37) Root-knot under General Diseases. 

2. Sooty Mold — Black moldy patches on the foliage. Control: Apply malathion to 
control scales, mealybugs, and other insects. 

ILEX -See Holly 

ILLICIUM-See Magnolia 

IMPATIENS-See Balsam 

INCENSE - CEDAR - See Juniper 

INDIAN CHERRY -See Buckthorn 



254 INDIAN-CUP 

INDIAN -CUP -See Chrysanthemum 

INDIAN CURRANT -See Snowberry 

INDIAN PAINTBRUSH - See Snapdragon 

INDIAN SHOT -See Canna 

INDIAN - TOBACCO - See Lobelia 

INDIA RUBBER PLANT or TREE - See Fig 

INDIGO (Indigofera), INDIGOBUSH - See False - indigo 

INKBERRY-See Holly 

INULA — See Chrysanthemum 

IPOMOEA — See Morning - glory and Sweetpotato 

IRESINE-See Cockscomb 

IRIS [ CRESTED, DANISH, DUTCH, DWARF, ENGLISH, JAPANESE or 
KAEMPFERI, SPANISH, SIBERIAN, TALL BEARDED or GERMAN, and ZUA ] 

(Iris); BABIANA; BLACKBERRY - LILY (Belamcanda); BLUE - EYED GRASS 
(Sisyrh'mchium); WANDFLOWER (Sparaxis); STREPTANTHERA; WATSONIA 

1. Crown, Rhizome, Bulb or Corm Rots, Root Rots — General and serious, especially 
on iris. Young fans may fail to grow in the spring. Leaves turn yellow, wither, and 
die. Leaves suddenly wilt and collapse or die back gradually from the tips. Rhizome 
or bulb, crown, and leaf bases may be dark green, slimy and foul-smelling (Bacterial 
Soft Rot), or covered with a cottony, gray or bluish mold growth, shriveled, dried, 
and rotted (fungus rots) . Roots may decay; be few or none. The newer iris hybrids 
appear more susceptible than the older varieties. See Figure 37C and Figure 43B 
under General Diseases, as well as Figure 127. Control: Plant firm, disease-free 
stock, shallow in clean or sterilized soil (pages 437-44) . Before planting, soak rhi- 
zomes or bulbs for 10 minutes in a 1:1,000 solution of mercuric chloride (see page 
427 for precautions) , Semesan solution (1 heaping tablespoonful per gallon) , or in 
a phenyl mercury solution for 30 minutes. Follow the manufacturer's directions. 
Space plants and plant in well-drained soil in a sunny location where these plants 
have not grown for at least several years. Dig and divide clumps every 2 to 4 years. 
Dry rhizomes or bulbs thoroughly in the sun for several days after digging. Avoid 
bruising when digging and cleaning. Avoid wounding leaves or flower stalks and 
overwatering. Keep down weeds. If rot strikes, dig up and burn plants that are 
seriously infected. Cut out the rotted areas of slightly infected rhizomes. Drench the 
the soil around infected plants using the same strength mercuric chloride (1 pint 
per square foot) or use Semesan (1 ounce in 3 gallons of water) . Phenyl mercury 
may also be applied following the manufacturer's directions. Repeat the drench 
treatment 10 days later. Control insects, especially iris borers, using DDT. Combine 
with Leaf Spot sprays (see below) . Certain fungus rots are controlled by mixing 
Terraclor (PCNB) dust into the top 4 to 6 inches of soil about a week before 
planting. Follow the manufacturer's directions. 

2. Leaf Spots, Blotch — General and serious. Small, grayish-brown to brown spots with 
water-soaked, yellowish, or dark brown margins on the leaves. Spots often enlarge 
and run together causing the leaves to turn yellow and die prematurely from the 
tip down. Spots may also occur on the stems and flower buds. Plants are gradually 



IRIS 



255 



weakened. See Figure 15A under General Diseases. Control: Same cultural prac- 
tices as for Crown Rots (above) . Cut off and burn heavily spotted leaves as they 
occur. Spray four to six times, 7 to 10 days apart, starting just before bloom. Use 
zineb, maneb, phaltan, captan, or phenyl mercury to which detergent or spreader- 
sticker is added (page 104) . Varieties differ greatly in susceptibility, especially 
iris. 
3. Mosaic, Stripe — General on dwarf iris and certain tall, bearded types. Also attacks 
other plants listed. Symptoms variable. Even masked in some varieties. Leaves and 




INK SPOT 



Iris bulb rots. 



bud sheaths are mottled light and dark green, or show light, yellowish-green 
streaks. Flowers may be mottled and streaked or fail to open. Plants and flowers 
may be stunted. See Figure 128. Control: Dig and burn infected plants when first 
found. Plant disease-free stock. Control aphids, which transmit the virus, using 
malathion or nicotine sulfate. 
4. Scorch, Red Fire (tall and dwarf bearded iris) — Central leaves turn a bright, red- 
dish-brown at the tips in early spring. Later the whole fan of leaves is "scorched" 
and withered. Roots are soft, dead, reddish, hollow, and later disintegrate. Rhizome 
becomes reddish colored. Plants often die. Nematodes are often found in the roots 
of affected plants. Control: Dig up and burn infected plants. Same as for Crown 
Rots (above) . Plant clean stock in soil fumigated with D-D, EDB, or chloropicrin. 
See pages 440-44 in the Appendix. 



256 



IRIS 



5. Bacterial Leaf Spot or Blight (iris, belamcanda) — Irregular, dark green, water- 
soaked spots and streaks on the leaves and flower stem. Infected areas enlarge, may 
run together and turn a yellowish-green and finally brown. Leaves and flower stem 
may collapse. See Figure 129A. Control: Same as for Leaf Spots (above) , except 
that spraying is ineffective. Avoid damp, shaded locations and crowding plants 
together. 

6. Rusts — More common on wild iris and cultivated varieties of Iris germanica type. 
Small, reddish-brown, dark brown or black, powdery pustules on the leaves and 
stems. Often surrounded with a yellowish border. Leaves of certain susceptible 
varieties may wither and die early. See Figure 129B. Control: Collect and burn the 
tops in the fall. Most iris varieties are highly resistant or immune. Keep down 
weeds. If severe enough, spray as for Leaf Spots (above) or use dichlone or ferbam. 

7. Blossom Blight (iris) — Blossoms spotted or blighted in wet weather. Control: Spray 
as for Leaf Spots (above) . Use zineb or captan. Pick off and destroy spotted flowers 
when first found. 

8. Bulb and Stem Nematode — Yellow spots or streaks on the stem and sheath. The 
base of the stem under the outer coating may turn gray, brown or lead-colored and 
streaked. Discolored areas appear as rings when bulbs are cut through. Infested 





HEALTHY 




PEELED 



DISEASED 




Fig. 129. A. Bacterial leaf spot of iris, B. 
Iris rust. 



Fig. 130. Iris bulb and stem nematode. 



plants may be stunted and dry up prematurely. Roots discolored, decayed, or 
lacking. Bulbs decay. See Figure 130. Control: Plant nematode-free stock in clean 
soil. If suspicious, treat dormant iris bulbs by soaking in hot formalin solution 1:200 
(1 teaspoonful of 37-40 per cent commercial formaldehyde in 1 quart of water) 
at 110° F. for 3 hours. Dry and plant as soon as possible. 
9. Meadow or Root-lesion, Lance, Root Plate, Pin, Spiral Nematodes — Plants dwarfed. 
May die from a rotting of the roots. Root system is often matted and "tufted." 



IVY 



257 



Younger, newer roots have small, reddish-brown spots on them. Rot organisms and 
blue mold often later destroy the infested bulb. Control: Plant nematode-free stock 
in soil pasteurized by heat or chemicals. Destroy badly infested plants. 

10. Root-knot — Knobby, beadlike galls or knots form on the roots. Plants may be 
dwarfed and sickly. Leaves die gradually, from the tips down. Control: Same as for 
Meadow Nematode (above) . 

W.Ink Disease, Leaf Blight (bulbous iris) —Irregular, ink-black stains, often ring- 
like, on outer skin of bulb scales. The blotches enlarge to cover the whole scale. 
Bulbs may turn black, shrivel, and become hard. Black, sooty blotches on the leaves 
which later turn reddish-brown. Leaves wither from the tip down. See Figure 127. 
Control: Destroy infected plants and infected leaves. Treat lightly infected bulbs 
as for Bulb Nematode (above) . Spray as for Leaf Spots (above) . Dig bulbs each 
year and replant in a new location. 

12. Blindness, Blasting (forced iris) —Flowers do not develop or flower buds do not 
open after forming. May be caused by rotting of underground parts, late digging, 
low curing or precooling temperature, small bulb size, and other factors. 

13. Chlorosis — Mineral deficiency in alkaline soil. See under Rose. 

IRONWOOD-See Birch 

IVY [ BALTIC, CANARY, ENGLISH ] (Hedera). IVY - See Grape for 
Boston, Engelmann, Grape, and Marine - ivy. See Snapdragon for 

Kenilworth ivy. 

I. Fungus Leaf Spots, Stem Spots, Twig Blight, Spot Anthracnose or Scab, Anthrac- 
nose — Small to large, round to irregular spots of various colors on the leaves and 
stems. Often with conspicuous margins. Stems may be blighted, wither and die 



Fig. 131. Leaf spots of English ivy. A. 

Bacterial leaf spot, B. Phyllosticta leaf 

spot. 




back. Infected leaves may wither and fall early. See Figure 131. Plants may appear 
ragged. Control: Where practical, pick off and burn infected plant parts. If severe, 
spray weekly using zineb, maneb, or fixed copper. Do not plant where high temper- 
atures and moist conditions are prevalent. 

!. Winter Injury, Sunscald — Foliage is scorched and browned in early spring. Control: 
Follow the best local cultural practices. Check with your extension horticulturist 
or landscape architect. Plant only where adapted. 

I. Bacterial Leaf Spot, Stem Canker — Common indoor problem, where moist. Small, 
round, light green, water-soaked spots on the leaves. Spots later enlarge, turn 
brownish-black, and develop reddish-purple borders. Black areas on the petioles 
or stems may cause girdling and withering of the portions beyond. Plants may be 
dwarfed, with sickly yellowish-green foliage. Control: Same as for Fungus Leaf 



258 IVY-ARUM 

Spots (above) . Apply fixed copper, bordeaux, or streptomycin. Indoors, keep water 
off the foliage. Space plants. Avoid high humidity. 

4. Powdery Mildew — See (7) Powdery Mildew under General Diseases. 

5. Sooty Mold — Common on ground cover under trees. The black mold grows on 
insect honeydew dropped from aphids feeding in the trees above. See (12) Sooty 
Mold under General Diseases. 

6. Root Rots — See (34) Root Rot under General Diseases. Often associated with 
root-feeding nematodes (e.g., lance, spiral, stem, stubby-root, stylet or stunt) . 

IVY -ARUM -See Calla 

IXIA-See Gladiolus 

IXORA — See Buttonbush 

JACARANDA-See Catalpa 

JACKBEAN - See Bean 

JACK - IN - THE - PULPIT - See Calla 

JACOBS -LADDER -See Phlox 

JACQUEMONTIA-See Morning-glory 

JADE PLANT -See Sedum 

JAPANESE LAWNGRASS - See Lawngrass 

JAPANESE PAGODATREE - See Honeylocust 

JAPANESE PLUM -YEW (Cephalotaxus) 

L Twig Blight — See under Juniper. 

JAPANESE SPURGE -See Pachysandra 

JASMINE [COMMON, ITALIAN, PRIMROSE, ROSY, WINTER] (Jasminum) 

1. Leaf Spots, Spot Anthracnose or Scab — Leaves spotted. May fall early. Control: 
Pick off and burn infected leaves. If serious enough, spray several times, 10 to 14 
days apart. Use zineb or maneb. 

2. Root Rots — Set under Apple, and (34) Root Rot under General Diseases. May be 
associated with root-feeding nematodes (e.g., burrowing) . 

3. Blossom Blight — See (31) Blossom Blight under General Diseases. 

4. Crown Gall — See (30) Crown Gall under General Diseases. 

5. Root-knot — See under Peach, and (37) Root-knot under General Diseases. 

6. Crown Rot, Southern Blight — See (21) Crown Rot under General Diseases. 

7. Rust — Uncommon. Leaves, stem, flowers, and fruit are deformed with raised, 
powdery pustules which later turn brown. Control: Same as for Leaf Spots (above) . 

8. Variegation, Infectious Chlorosis — See under Hollyhock. 

9. Stem Gall — Small galls occur on stems. Control: Cut out and burn affected parts. 
Spray as for Leaf Spots (above) . 

JERUSALEM - ARTICHOKE - See Lettuce 

JERUSALEM -CHERRY -See Tomato 



JUNIPER 259 



JERUSALEM -CROSS -See Carnation 
JERUSALEM - THORN - See Honeylocust 

JESSAMINE - See Butterflybush 
JETBEAD, WHITE KERRIA (Rhodotypos) 

1. Leaf Spot, Anthracnose — Leaves spotted in rainy seasons. Control: Pick off and 
burn infected leaves. If serious enough, spray several times, 10 to 14 days apart, 
using zineb, ferbam, or captan. 

2. Twig Blight, Coral Spot — Twigs die back. Cankers on affected parts may be 
covered with bright, coral-colored pustules. Control: Cut out and burn blighted 
twigs. Fertilize and water to maintain good vigor. 

3. Fire Blight — See under Apple. 

JOE -PYE- WEED -See Chrysanthemum 

JOSEPHSCOAT - See Cockscomb 

JOSHUA -TREE -See Yucca 

JUDAS -TREE -See Honeylocust 

JUGLANS-See Walnut 

JUNEBERRY-See Apple 

JUNGLEFLAME - See Buttonbush 

JUNIPER [ALLIGATOR, ANDORRA, CHINESE (COLUMNAR, GLOBE, HETZ 
BLUE, PYRAMIDAL), COMMON (DWARF SWEDISH, SWEDISH), CREEPING, 
GREEK, HILL, IRISH, JAPANESE, JAPANESE SHORE, MOUNTAIN, MEYER'S, 
NEEDLE, PFITZE*, PROSTRATE, ROCKY MOUNTAIN, SAVIN, WAUKEGAN], 
CREEPING CEDAR, REDCEDAR [ CANAERT, CREEPING, EASTERN, 
FOUNTAIN, GLOBE, GOLDTIP, HILL'S PYRAMIDAL, KETELEER, KOSTER, 
SCHOTT, SILVER, SOUTHERN, WEEPING, WESTERN] (Juniperus); WHITE- 
CEDAR [ATLANTIC, SOUTHERN], LAWSON or PORT ORFORD CEDAR; 
YELLOW -CEDAR [ALASKA or NOOTKA], HINOKI CYPRESS, SAWARA - 
CYPRESS (Chamaecyparis or Refinospora;,- CRYPTOMERIA: CYPRESS 
[ ARIZONA, COLUMNAR ITALIAN, ITALIAN, MONTEREY ] (Cupressus); 
INCENSE CEDAR (Lbocedrus); ARBORVITAE [AMERICAN (numerous 
horticultural forms), EASTERN or NORTHERN WHITE-CEDAR (numerous 
horticultural forms), BLACK AMERICAN, GIANT, DARK GREEN GIANT, 
COLUMNAR GIANT, GLOBE, GOLDEN, GOLDEN BIOTA, JAPANESE, 
KOREAN, ORIENTAL, PYRAMIDAL, SILVER] (Thuja); HIBA ARBORVITAE, 
DWARF HIBA ARBORVITAE (Thujopsis) 

I. Rusts, Gall Witches' -broom (primarily chamaecyparis, incense-cedar, juniper, red- 
cedar) — General. Upright junipers (redcedars) are susceptible while prostrate or 
horizontal types are generally resistant. Greenish-brown to reddish-brown, bean- 
shaped galls (up to 2 inches in diameter) or witches'-brooms on small branches. 
The tips of the branches may die back. Elongated, rough, dark-colored, swollen 
cankers (or burls) may develop on the larger branches and trunk. Masses of orange 
to brown-colored, jellylike tendrils are produced in wet spring weather. 
Chamaecyparis seedlings may be severely stunted. See Figure 22D under General 



260 JUNIPER 

Diseases. A large number of alternate hosts, some of which are listed under Apple. 
Other hosts include bayberry, sweetfern, and waxmyrtle. Control: Destroy worth- 
less, upright junipers or alternate hosts. If practical, hand pick galls or prune out 
witches'-brooms by late winter or spray monthly, May to September, using Acti- 
dione or a mixture of ferbam and sulfur. Spray with Acti-dione, Elgetol, or Krenite 
when tendrils are 1/16 of an inch out. Follow the manufacturer's directions. 

2. Twig Blights, Needle Blight, Dieback — Widespread. Needles, twigs, and smaller 
branches turn light brown to reddish-brown and gradually die back from the tips. 
Both old and new leaves and twigs may be involved. Serious on seedlings and 
young trees in wet seasons. Entire branches or even trees may be killed. Tiny black 
dots usually appear later on infected parts. Often confused with normal fall brown- 
ing of the inner leaves, winter injury, and damage from spider mites. Control: 
Prune out and burn blighted parts. Destroy infected plants in the nursery. Avoid 
wounding when transplanting or cultivating. Apply phenyl mercury, fixed copper, 
captan, maneb, or Acti-dione, plus spreader-sticker (page 104) at about 1- to 2-week 
intervals during spring and fall wet seasons. Follow the manufacturer's directions. 
Space plants to provide good air circulation. Avoid overhead sprinkling in the 
nursery. Somewhat resistant junipers: Spiny Greek, Hill, and Keteleer redcedar. 

3. Leaf Blights, Seedling Blight, Nursery Blights, Needle Cast (primarily American 
and giant arborvitae) — Widespread and damaging. Small, round to irregular, 
olive-brown to black cushions form on the leaves in late spring. The infected leaves 
appear scorched. Later the leaves drop. Branches are left bare. Most common on 
the bottom 2/ s of young trees. Control: Same as for Twig Blights (above) . Resistant 
arborvitae varieties may be available soon. 

4. Winter Injury — General. Last year's foliage is scorched, turns brown and dies back 
from the tips and margins. Injury is evident in late winter and spring. Heavy 
coatings of ice and snow may seriously injure or kill if allowed to remain on 
trees and shrubs. Control: Water shrubs deeply in the fall, and during dry 
periods. Mulch plants for winter to conserve moisture, prevent deep freezing plus 
alternate thawing and freezing of the soil. Plant in a location protected from drying 
winter winds and sun or erect protective screens made of burlap, canvas, or other 
material. Control mites with malathion or other sprays. Grow chamaecyparis only 
where adapted. 

5. Twig and Branch Cankers — Serious on Monterey and Italian cypress in California. 
Discolored, slightly sunken cankers on the twigs and branches which gradually girdle 
and kill the portions beyond. Branches or entire trees drop their yellowed and 
browned leaves and finally die. Control: Prune off affected parts well below the 
cankers. Spray as for Twig Blights (above) . 

6. Natural Leaf-browning and Shedding — Noticeable on arborvitae and certain 
junipers. Older and inner leaves turn brown and fall in large numbers in early 
to late fall. May occur quite suddenly in a week or two. Control: This is a normal 
plant reaction. 

7. Chlorosis — Occurs in alkaline soils. See under Maple. 

8. Sooty Mold, Black Mildews — See (12) Sooty Mold under General Diseases. 

9. Wood and Heart Rots — Cosmopolitan. See under Birch, and (23) Wood Rot un- 
der General Diseases. 

10. Crown Gall — See under Apple, and (30) Crown Gall under General Diseases. 

M.Root Rots — Foliage often wilts and changes color. Branches or top dies back. 
Trees of all ages gradually decline and die from rot in the trunk base and larger 
roots. Very serious on Port Orford cedar or Lawson cypress and Hinoki cypress 
along the Pacific Coast. Control: See under Apple. Nurserymen grow disease-free 



LABRADOR-TEA 261 



stock in new or sterilized soil. Avoid large plantings of Port Orford cedar or Hinoki 
cypress as windbreaks or hedges. Remove and destroy affected plants, including 
the roots. 

12. Mistletoes — Widespread. See (39) Mistletoe under General Diseases. Serious on 
incense-cedar, causing spindle-shaped swellings in the branches. 

13. Brown Felt Blight, Snow Blight (juniper, arborvitae) —See under Pine. 

14. Root-feeding Nematodes (dagger, lance, pin, spiral, stubby-root, stylet or stunt, 
ring, root-lesion) — Associated with stunted, sickly trees in a state of decline. See 
under Peach. 

JUPITERS- BEARD -See Valerian 

KALANCHOE - See Sedum 

KALE — See Cabbage 

KALMIA, KALMIOPSIS - See Blueberry 

KALOPANAX — See Acanthopanax 

KANGAROO VINE - See Grape 

KENILWORTH IVY - See Snapdragon 

KENTUCKY COFFEETREE - See Honeylocust 

KERRIA 

l.Leaf and Twig Blight, Leaf Spots, Canker — Widespread. Small, round to irregu- 
lar, light to reddish-brown spots with a darker margin on the leaves. If spots are 
numerous, leaves turn yellow and die prematurely. Spots (cankers) on the stems 
are round and reddish-brown to black in color. The spots may run together 
forming large cankers. The bark may split and twigs die back. The dwarf, varie- 
gated Kerria is very susceptible. Control: Prune off and burn affected parts. Col- 
lect and burn fallen leaves. Spray or dust several times, 10 days apart, starting 
when the leaves are 14 inch long. Use zineb, ferbam, maneb, or fixed copper. 

2. Twig Blights, Canker — Widespread. Oval to elongated or irregular, tan-colored 
spots on the stems. The centers of the spots may be sprinkled with tiny black 
dots or bright, coral-red pustules. Twigs may die back. Leaves may become blighted. 
Control: Same as for Leaf and Twig Blight (above) . 

3. Root Rot — See (34) Root Rot under General Diseases. 

4. Fire Blight — See under Apple. 

KNIPHOFIA-See Redhot - pokerplant 

KOCHIA-See Beet 

KOELREUTERIA - See Goldenrain - tree 

KOHLRABI -See Cabbage 

KOLKWITZIA - See Viburnum 

KUMQUAT-See Citrus 

LABRADOR -TEA (Ledum); LEUCOTHOE [COAST, DROOPING, 
SWEETBELLS] aeucofhoe;,- BOX SANDMYRTLE (Leiophyllum) 

l.Leaf Galls — Gall-like growths and red spots on the leaves. Control: Prune and 
burn infected parts when first seen. Plant disease-free stock. If necessary, apply a 



262 



LABRADOR-TEA 



dormant spray before buds swell. Repeat applications during wet periods. Use 
ferbam, zineb, or maneb. 

2. Spot Anthracnose (Labrador-tea, leucothoe) —Not serious. Grayish-white spots 
on the leaves with reddish-brown borders and zoned with a purplish ring. Infected 
areas also appear on the capsules, petioles, and branches. Control: Pick off and 
burn infected parts. Spraying with zineb or maneb should give good protection. 

3. Rusts (Labrador-tea) —Causes little injury. Powdery pustules on the leaves. Al- 
ternate hosts are spruces. Control: Not necessary. Spraying as for Spot Anthracnose 
and Leaf Galls (both above) should be beneficial. 

4. Leaf Spots, Tar Spot, Black Spot — Spots of various sizes, shapes, and colors on 
the leaves. The centers of the spots may later be sprinkled with black dots. See 




Fig. 132. Leucothoe leaf spots. 



Figure 132. Control: Pick off and burn infected leaves. Where serious, apply fer- 
bam or zineb at 10- to 14-day intervals, starting when the new leaves are 14 inch 
out. 

5. Black Mildew (leucothoe) -Gulf states. See (12) Sooty Mold under General Dis- 
eases. 

6. Felt Fungus (leucothoe) — Southern states. See under Hackberry. 

7. Powdery Mildew (Labrador-tea) —See (7) Powdery Mildew under General Dis- 
eases. 



LANTANA 263 



LABURNUM -See Goldenchain 

LACHENALIA - See Tulip 

LADYS - SORREL - See Oxalis 

LAELIA-See Orchids 

LAGENARIA - See Cucumber 

LAGERSTROEMIA - See Crapemyrtle 

LAMBKILL-See Blueberry 

LAMBS - EARS - See Salvia 

LAMBSLETTUCE - See Valerian 

LANTANA [TRAILING, WEEPING] (Lantana); LEMON - VERBENA, 

FOGFRUIT, WHITEBRUSH (Llppla); BEAUTYBERRY, FRENCH -MULBERRY, 

JEWELBERRY [JAPANESE. KOREAN, GIRALD'S or BODINIER 

BEAUTYBERRY] (Callicarpa); BLUEBEARD, BLUE MIST SPIREA (Caryopteris); 

GLORYBOWER (Clerodendron); PHYLA; GARDEN VERBENA, VERVAIN 

(Verbena); CHASTE - TREE (Vitex) 

1. Root-knot — Widespread. See (37) Root-knot under General Diseases. 

2. Leaf Spots, Anthracnose , Spot Anthracnose — Small to large spots of various colors 
and shapes on the leaves. Control: Pick off and burn spotted leaves. Spray at 7- 
to 10-day intervals during wet periods. Use zineb, maneb, or captan. 

3. Leaf Nematode (lantana, verbena) — Brown blotches on the leaves. First bounded 
by the veins. Later the leaves are killed, starting at the base of the stem. Control: 
See under Chrysanthemum, and (20) Leaf Nematode under General Diseases. 

4. Stem Rot, Blight — See under Geranium. 

5. Black Mold or Mildew — See (12) Sooty Mold under General Diseases. 

6. Fusarium Wilt (lantana) —See (15A) Fusarium Wilt under General Diseases. 

7. Powdery Mildew (verbena) — General. Powdery, white mold growth on the leaves 
and stems. Control: Space plants. Apply two sprays of Kara thane, 10 days apart. 

8. Rusts (lantana, verbena) — Small, yellow to dark brown pustules on the leaves. 
Alternate host may be wild grasses. Control: Where practical, same as for Leaf 
Spots (above) . 

9. Bacterial Wilt (verbena) — Leaves turn yellow, wilt, and die. Plants often die be- 
fore blooming. Inside of stems is dark brown near the soil line. Control: Set 
disease-free plants in clean or sterilized soil (pages 437-44) . 

10. Flower Blight (verbena) — Flower petals spotted, may rot. Affected areas are cov- 
ered with a dense gray mold in damp weather. Control: Carefully pick off and 
burn spotted flowers. Spray as for Leaf Spots (above) . 

11. Spotted Wilt (verbena) —See (17) Spotted Wilt under General Diseases. 

12. Downy Mildew (verbena) —See (6) Downy Mildew under General Diseases. 

13. Gray Patch (phyla) —California in hot weather. Ground cover plants dry out 
and die in patches a foot or more in diameter. Control: Try working Terraclor dust 
into the soil in affected areas or spot drench with Terraclor 75. Follow the manu- 
facturer's directions. 

14. Mosaic (lantana, verbena) — Light green and yellow mottling on the leaves. 
Leaves may be somewhat crinkled and distorted. Control: Destroy infected plants. 



264 LARCH 

15. Dieback, Canker (callicarpa) — See under Apple. 

16. Root Rots — See (34) Root Rot under General Diseases. May be associated with 
nematodes (e.g., burrowing, root-knot) . 

17. Crown Gall (lippia) — See (30) Crown Gall under General Diseases. 

LARCH [ALPINE, AMERICAN, EASTERN, EUROPEAN, JAPANESE, 
WESTERN ], TAMARACK (Larix); GOLDENLARCH (Pseudolarix) 

l.Leaf Casts, Needle and Shoot Blights — Primarily American and western larches. 
Needles are spotted, turn yellow then reddish-brown. Needles and shoot tips die 
back. Needles usually fall prematurely but some may cling over winter. Infected 
needles may be sprinkled with tiny white to black dots. Control: Gather and burn 
fallen needles in late autumn. If practical, spray ornamental larches several times, 
2 weeks apart, using zineb, captan, maneb, fixed copper, bordeaux mixture, or lime- 
sulfur. Start when new growth is commencing. 

2. Needle Rusts — Small, pale yellow to bright orange pustules on the new needles. 
Needles turn yellow, may be distorted and fall early. Causes little damage. Al- 
ternate hosts include willows, poplars (and aspens) , birches, and alders. Control: 
Where practical, destroy nearby, worthless, alternate hosts. If serious enough, 
spray larches several times, 10 days apart, using zineb or ferbam. Start applica- 
tions just before apple trees bloom. 

3. Wood Rots — Cosmopolitan. Mostly occur on older, neglected trees which lack 
vigor. See under Birch, and (23) Wood Rot under General Diseases. 

4. Twig Blight — Tips of new growth develop dead, curled leaves during cold, wet 
weather. A gray mold may cover affected areas. Control: Prune and space plants 
for better air circulation. 

5. Root Rots — Cosmopolitan. Trees decline in vigor. Foliage is thin and sickly. Leaves 
may turn yellow, wither, and drop early. Control: See under Apple, and (34) Root 
Rot under General Diseases. 

6. Frost Injury — Needles turn completely brown all at once. Shoot tips are usually 
most seriously affected. Needles later shrivel but tend to remain on the twigs for 
the balance of the season. 

7. European Larch Canker (especially American and European larches, Golden- 
larch) — Northeastern states, but believed to be eradicated. Cankers on larger trees 
develop gradually from year to year appearing as flattened, sunken, bowl-like, dead 
areas in the bark on the trunk or branches. Large amounts of resin may flow from 
cracked areas. Trees are distorted, swollen, and weakened. Stems and branches of 
young trees are quickly girdled and killed. The Japanese larch is relatively re- 
sistant. Control: Maintain trees in good vigor by proper fertilization and watering 
during dry periods. Plant in full sun in moist, well-drained soil. Avoid dry locations 
(e.g., sandy hillsides) and wounding or injuring the bark. Treat all bark wounds 
promptly with tree wound dressing (page 25) . Cut down and burn all infected 
trees. If you suspect canker, contact your state or extension plant pathologist. 

8. Dwarf Mistletoes — Northeastern and northwestern states. See (39) Mistletoe under 
General Diseases. 

9. Seedling Blight, Damping-off — Seedlings are discolored and stunted. Often wilt 
and collapse. Control: Treat seed with thiram, captan, or dichlone. Plant in clean, 
well-drained soil. Avoid overwatering. Keep down weeds. Where practical, sterilize 
the soil before planting, using heat or chemicals (pages 437-44) . 



LAWNGRASS 



265 



LARKSPUR -See Delphinium 

LATHYRUS-See Pea 

LATUCA-See Lettuce 

LAUREL, MOUNTAIN -See Blueberry 

LAVATERA-See Hollyhock 

LAVENDER (Lavandula) - See Salvia 

LAVENDER QUEEN -See Snapdragon 

LAWNGRASS: WHEATGRASS (Agropyron); BENT, BENTGRASS, REDTOP 

(Agrostis); CARPETGRASS (Axonopus); BUFFALOGRASS (Buchloe); 

BERMUDAGRASS (Cynodon); CENTIPEDEGRASS (Eremochloa); 

FESCUE, FESCUE GRASS (Festuca); RYEGRASS (Lolium); BLUEGRASS (Poa); 

ST. AUGUSTINE GRASS (Stenotaphrum); ZOYSIA, ZOYSIAGRASS, 

JAPANESE LAWNGRASS, MANILAGRASS (Zoysia) 

I. Leaf Spots and Blights, Melting-out, Dying-out, Fade-out, Anthracnose — General. 
Purplish-black, dark brown, light gray, or tan spots on the leaves, leaf sheaths, and 
stems. Spots may be round, oval, or oblong in shape. With or without a prominent 
border. Usually follows cool, moist weather. Spots may enlarge and develop light- 
colored centers. Older leaves or entire plants may turn yellow, then brown and die. 



Fig. 133. Leaf spot of Kentucky bluegrass. || 
(Courtesy Upjohn Co.) 




Crowns and roots turn brown and rot. See Figure 133. Infected areas may have a 
general brownish undercast. Turf is thin and weak or killed out in round to 
irregular spots which enlarge during the summer. Control: Avoid heavy watering, 
frequent sprinkling, and overstimulation with fertilizer (especially with nitrogen) 
during the summer months. If practical, collect clippings. Mow regularly at the 



266 



LAWNGRASS 



height recommended for your area. Grass varieties differ in resistance. Apply phenyl 
mercury (but not to Merion bluegrass) , Thimer, Tersan OM, Kromad, zineb, 
captan, phaltan, Acti-dione-thiram mixture, Ortho Lawn and Turf Fungicide, or 
Dyrene at 2-week intervals during spring, wet weather and continuing through 
July. Follow the manufacturer's directions. Mercury-containing fungicides fre- 
quently injure strictly southern grasses. Check with a lawn specialist. Soil drenches 
of zineb or captan (1 pound per 1,000 square feet), well watered in, are used 
by golf course superintendents to control Melting-out. Make several weekly appli- 
cations starting in midspring. Apply chlordane (2 pounds actual) in 2 to 5 gallons 
of water per 1,000 square feet of lawn in early spring as grass starts to grow. This 
treatment controls crabgrass, earthworms, grubs, cutworms, sod webworms, ants, 
chiggers, mites, and fleas. 

Powdery Mildew — General. Mostly on bluegrasses, fescues, and wheatgrass. Milky- 
white, grayish-white to brown mold patches on the leaves in shaded or poorly 



w 




Fig. 134. Bluegrass powdery mildew. Fig. 135. Rust on Merion bluegrass. (Cour- 
(Courtesy Upjohn Co.) tesy Upjohn Co.) 



drained areas. Disease attacks occur chiefly in spring and fall during periods when 
nights are cool and days are warm. Leaves may turn yellow and wither. Plants may 
be weakened and die. Most serious on new plantings. See Figure 134. Control: If 
necessary, make two applications of sulfur, Karathane, or Acti-dione-thiram mix- 
ture, 10 days apart. Water and fertilize to maintain vigor. Follow the cultural prac- 
tices as for Brown Patch (below) . 

Rusts (primarily Merion bluegrass, Bermudagrass, ryegrass, and St. Augustine 
grass) — General. Yellow-orange, reddish-brown, brownish-yellow or black, powdery 
pustules on the leaves and leaf sheaths. If severe, leaves may turn yellow, wither, 
and die. Turf may be thinned and weakened. Such turf is more susceptible to 
drought, winter injury, and other diseases. See Figure 135. Control: Fertilize with 
nitrogen and water deeply so grass is kept growing normally during the summer 
months. Otherwise apply zineb, Acti-dione-thiram mixture, maneb, dichlone, Kro- 



LAWNGRASS 



267 



mad, or thiram several times 7 to 10 days apart. Remove clippings if possible. Grow 
rust-resistant grasses. 

Brown Patch, Rhizoctonia Disease — More or less circular patches, up to 3 feet in 
diameter, often with a grayish-black margin (especially on bentgrass) . Grass leaves 
are first water-soaked, but soon dry, wither, and turn light brown. Roots and 
crowns may rot, especially in southern states. Turf may be thinned out in large 
areas, especially on southern grasses. Active in hot, humid weather when night 
temperatures are above 70° F. Bentgrasses are more seriously injured than coarser 
grasses. Control: Avoid overwatering and frequent sprinkling in late afternoon and 
evening. Prune dense trees and shrubs to increase air circulation. Avoid overferti- 
lization during the summer months with a quickly available, high-nitrogen fertilizer. 
Provide for good soil drainage when establishing a new lawn. If possible remove 
the clippings after each mowing. Spray weekly in hot, humid weather using Calo- 
cure, Ortho Lawn and Turf Fungicide, Tersan OM, Thimer, or Calocure-thiram 
mixture. Terraclor (PCNB) 75 per cent has given good control on St. Augustine 
grass. Follow the manufacturer's directions. 

Dollar Spot — Round, brown, bleached spots about the size of a silver dollar, to 
somewhat larger. Active in warm (60° to 85° F.) , moist weather. Spots may run 
together forming large, irregular, straw-colored, sunken areas. See Figure 136. Con- 




Fig. 136. Dollar spot. (Courtesy E. I. Du Fig. 137. Slime mold on Kentucky blue- 
Pont de Nemours & Co., Inc.) grass. (Courtesy Upjohn Co.) 



trol: Spray during the spring months and again in late summer and fall using 
Tersan OM, Thimer, Cadtrete, Panogen Turf Spray, Kromad, Caddy, Cadminate, 
phenyl mercury, Dyrene, Ortho Lawn and Turf Fungicide, Calocure, or Acti- 
dione-thiram. Follow the manufacturer's directions. Creeping bents are most sus- 
ceptible. Maintain adequate to high fertility by following the recommended lawn 
feeding program for your area. Collect clippings. Same cultural practices as for 
Brown Patch (above) . 
6. Slime Molds — General. Small, colorless, white, gray, or yellow slimy masses grow 
up and over the grass surface in round to irregular patches, smothering or shading 
otherwise healthy turf. The masses dry to form bluish-gray, gray, black, or white 
powdery growths which can be easily rubbed off the grass blades. Slime molds sud- 
denly occur following heavy watering or rains. Technically not a disease. See Figure 
137. Control: Mow, rake, or brush affected areas and wash down with water. Spray 
as for Leaf Spots or Rusts (both above) if desired. 



268 



LAWNGRASS 



7. Fairy Rings, Mushrooms (or "Toadstools") , Puff balls — Rings or arcs of dark 
green, fast-growing grass which range in size from several inches to 50 feet or more 
in diameter. Sometimes an inner ring of thin or dead grass occurs. Fairy rings ex- 
pand outward at a rate of a few inches to 2 feet or more per year. Toadstools, mush- 
rooms, or puffballs may spring up around the edge of the ring following heavy 
watering or rains. See Figure 138. Dry patches in turf areas may actually be in- 
fested with the spawn of these fungi. Control: Bore holes i/ 2 to 1 inch in diameter, 




Fig. 138. Fairy ring. Note dead areas in lawn and mushrooms (Lepiota morgani). 

(Courtesy Dr. W. H. Bragonier) 

4 to 5 inches apart, and at least 6 inches deep in the ring of stimulated grass and 
about 6 inches outside the ring. Fill the holes with a solution of Calo-clor, Calocure, 
Fungchex, or Woodridge Mixture 21 (2 ounces in 5 gallons) , or use phenyl mercury 
according to the manufacturer's directions. Usually this is 1 to 2 ounces in 5 gallons 
of water. Add 2 ounces of household detergent per 5 gallons of water to aid in 
penetration. Use a battery bulb or funnel in filling the holes to avoid spilling 
the mercury solution on the grass. Water in the chemical liberally. Repeat the 
treatment monthly for a season. Or remove the sod and sterilize the soil beneath 
using a soil fumigant (pages 440-44) . Keep the lawn well fertilized and watered so 
that rings do not show so distinctly. 
8. Snow Scald, Gray Snow Mold — General in northern states. More or less circular, 
dead, bleached areas, up to about 2 feet in diameter. May be covered at first with 
a bluish-gray to almost black mold growth. Found in winter or early spring in 
shaded, wet areas or where snow is slow to melt. Usually associated with melting 
snow. A crustlike mat may form where the grass has been left long. See Figure 139. 
Control: In northern states avoid fertilizing after about September 15. Before the 



LAWNGRASS 269 



Fig. 139. Snow mold. (Courtesy E. I. Du 
Pont de Nemours & Co.. Inc.) 




first heavy snow is forecast or before cold drizzly weather apply Tersan OM, Thimer, 
Calocure, Calo-clor, thiram, or phenyl mercury following the manufacturer's direc- 
tions. Repeat during a midwinter thaw. Spray during the growing season as for 
Leaf Spots, Brown Patch, and Dollar Spot (all above) . 
9. Fusarium Patch, Pink Snow Mold — Small, round, brown patches, usually 1 to 2 
inches in diameter. Spots may sometimes enlarge to a foot or more across. May be 
covered at first with a white to pink mold growth. Usually associated with melting 
snow but attacks also occur during cold, drizzly weather (up to about 65° F.) . 
Control: Same as for Snow Scald (above) . Phenyl mercury and Caddy applied 
alternately at 2-week intervals during the spring and autumn, and monthly during 
the rest of the year, in western Washington gave excellent control. Somewhat re- 
sistant bentgrasses: Penn-cross, Cohansey, and Pennlu. Liming increases the severity 
of disease. 

10. Grease Spot, Spot Blight, Pythium Disease, Cottony B Ugh t — Widespread and de- 
structive in the southeastern states. Round, reddish-brown spots, several inches in 
diameter, with blackened, greasy borders. Occurs in hot, muggy weather (90° to 
110° F.) on heavy, poorly drained areas. Spots often run together to form 
streaks. The disease is apparently spread by mowing and flowing water. Spots dry 
out and become bleached. The disease may spread rapidly, killing out turf. In 
southern states, small white spots, which later become "cottony" are common, 
especially on ryegrass during the late fall, winter, and early spring. The roots are 
usually attacked and die back. Control: Follow the cultural practices as for Brown 
Patch (above) . Apply mitxure of Acti-dione and captan or zineb or use Dexon, cap- 
tan, zineb, Acti-dione, or Kromad alone during hot, humid periods. Start spraying 
with the first evidence of disease. Frequent applications are necessary (1 or 2 per 
week) . Follow the manufacturer's directions. In the southeastern states where 
Cottony Blight is severe, check with your extension or state plant pathologist for 
recommendations. Apply Dexon when planting ryegrass. Repeat 1 week later. 

11. Root-feeding Nematodes (awl, burrowing, cyst, cystoid, dagger, lance, needle, pin, 
reniform, ring, root-lesion or meadow, sheath, sheathoid, spiral, stem, sting, stubby- 
root, stunt or stylet) — Turf lacks vigor. Often appears stunted and yellowed with 
dead and dying areas. Injury is easily confused with fertilizer burn, a soil deficiency, 
poor soil aeration, drought injury, insects, and other types of injury. Grass may 
appear sickly and off-color. Does not respond normally to water and fertilizer. Grass 



270 LAWNGRASS 

blades dying back from the tips may be interspersed with apparently healthy 
leaves. Roots may be swollen, stunted, bushy, "stubby," and dark in color. Turf 
may later thin out, wilt, and "melt out." Severity of symptoms varies with the 
population of nematodes feeding on the roots. Plant parasitic nematodes can be 
identified only by taking suspected turf plugs and subjecting them to an analysis 
by a competent nematologist. Control: Keep grass growing vigorously by watering 
and fertilizing as recommended for your area. If necessary, apply soil drenches of 
Nemagon, Fumazone, or VC-13 Nemacide following the manufacturer's directions. 

12. Chlorosis, Yellowing — A problem in moderately to highly acid or alkaline soils. 
Turf areas are irregularly yellowed and stunted. Caused by a minor element defi- 
ciency, usually iron. Control: Apply 34 to 1 pound of iron sulfate or iron chelate 
(Versenol Iron Chelate, Sequestrene Iron Chelate) in 5 to 10 gallons of water per 
1,000 square feet. Repeat the treatment as necessary to maintain normal green turf 
color. Some lawn fungicides (e.g., Kromad, Formula Z, and Acti-dione Ferrated) 
already have iron sulfate in the spray mixture. 

13. Algae, Green Scum — A green to blackish scum forms on bare soil or thinned turf. 
Occurs in low, wet, shaded, or heavily tracked and compacted spots. Technically not 
a disease. Dries to form a thin, black crust which later cracks and peels. Control: 
Same cultural practices as for Brown Patch (above) . Provide for good soil drain- 
age. Aerify. Maintain turf in good vigorous condition. Where necessary, apply a 
spray of copper sulfate, 2 ounces in 3 to 5 gallons of water to 1,000 square feet of 
lawn. 

14. Smuts — General. Long or short stripes or spots in the leaves which rupture and 
release dark brown or black powdery masses. Leaf tissues may be shredded and 
withered. Control: Dig out and burn affected plants, where practical. Merion and 
Kentucky are more susceptible than other bluegrasses. Spring or fall soil drenches 
of nabam (1 part of 22 per cent nabam in 400 of water) appears promising. Zineb 
may also be effective. 

15. Red Thread, Pink Patch — Northern coastal regions, mostly on fescues, bents, blue- 
grasses, and ryegrass. Pink patches of dead grass 2 to 6 inches or more in diameter 
develop during cool, rainy weather in spring and fall. Usually only the leaves are 
affected. If severe, patches turn brown and plants die. Characteristic bright coral- 
pink to red threads "bind" leaves together in moist weather. Control: Maintain 
adequate fertility. Same chemicals as for Dollar Spot (above) . Apply at about 2- 
week intervals. Collect clippings. 

16. Copper Spot (bents, redtop) — Humid coastal areas in acid soils. More or less 
circular, coppery-red to orange spots, 1 to 3 inches in diameter. Spots may run to- 
gether forming irregular, copper-colored areas. Disease attacks occur during warm 

(65° to 85° F.) , wet periods. Control: Apply phenyl mercury, Calocure, Caddy, 
Ortho Lawn and Turf Fungicide, Cadminate, Thimer, Cadtrete, or Kromad accord- 
ing to the manufacturer's directions. 

17. Gray Leaf Spot of St. Augustine Grass — Destructive in hot or humid periods. Small 
brown dots on the leaves which later enlarge to form roundish, dirty-yellow, or 
ash-colored leaf spots and stem cankers with reddish-brown, purple, or water-soaked 
borders. Spots may be covered with a grayish mold in humid weather. Turf is 
unsightly and more susceptible to drought and other types of damage. Control: 
Apply phenyl mercury, Calocure, Thimer, Tersan OM, captan, Kromad, chloranil, 
or thiram at 8- to 10-day intervals following the manufacturer's directions. 

18. Fusarium Blight of Bluegrass — Northeastern states. Small tan or straw-colored 
spots develop in lawns in early summer. Spots later enlarge and run together caus- 
ing large areas of the lawn to turn brown. Control: Same as for Leaf Spots (above) . 



LAWNGRASS 271 



19. Spring Dead Spot of Bermudagrass — Apparently fairly widespread in well cared 
for turf. Conspicuous, bleached, round dead spots are present in the spring. Spots 
vary in size from a few inches to 3 or more feet in diameter. Roots are black and 
rotted. Sometimes the center of the spots may survive resulting in "doughnuts." 
Spots usually remain dead for a number of years. Such areas become invaded by 
weeds and other grasses. Disease is most severe on U-3 Bermudagrass although 
African, Common, Tiffine, and Tifgreen are also infected. May be confused with 
snow mold, winter, or insect injury. Control: Dieldrin soil drenches in late fall and 
early winter have proved effective. Check with your state or extension plant path- 
ologist. 

20. Moss — Occurs in lawn areas low in fertility with poor drainage, high soil acidity, 
too much shade, watered improperly, heavily compacted, or a combination of 
these factors. Control: Remove by hand raking. Follow the cultural practices as for 
Brown Patch (above) and Compacted Areas (below) . Have a soil test made and 
follow the instructions in the report. 

2\.Seed Rot, Seedling Blight, Damping-off — General. Seeds rot. Stand is thin in 
patches. Seedlings stunted, water-soaked, then turn yellow to brown. May wilt and 
collapse. Surviving plants are weakened. Stand is slow to fill in. Control: Plant fresh, 
best quality seed in a well-prepared seedbed of high fertility. Provide for good soil 
drainage when establishing a new lawn. Treat seed with captan or thiram. Avoid 
overwatering after planting. If possible, plant in late summer or early fall. After 
sowing, apply a dilute spray of Kromad, captan, thiram, or zineb (4 ounces in 3 
gallons of water to cover 1,000 square feet) . Avoid low spots in the seedbed. 

22. Chemical Burning — Agricultural chemicals (e.g., fertilizers, pesticides, and hy- 
drated spray lime) may injure grass if improperly applied. Burned areas may 
occur in spots or streaks, or the entire lawn may be "scorched." Prevent injury by 
following the instructions printed on the package label. Apply fertilizers evenly in 
recommended amounts when the grass is dry. Then water in the fertilizer im- 
mediately. The use of a lawn spreader is highly recommended. Ground agricul- 
tural limestone is safer to use on lawns than hydrated lime. 

23. Female Dog Injury — Injury from dog urine may resemble brown patch or snow 
mold. Affected areas are often more or less round and up to a couple of feet in 
diameter. Injured grass turns brown or straw-colored and usually dies. 

24. Buried Debris — A thin layer of soil over buried rocks, lumber, bricks, plaster, or 
concrete dries out rapidly in dry summer weather and may resemble disease. Dig up 
suspicious areas and remove the cause. 

25. Compacted Areas — Thin turf or bare spots in heavily tracked areas. Waterlogged 
and heavy-textured soils become packed and later bake hard if walked on con- 
stantly. Correct by aerifying the soil using a hand aerifier or tined fork. Aerating 
machines are sold or rented by garden supply stores as well as by many nurserymen 
and golf courses. If necessary, fertilize and reseed. Reduce foot traffic by putting 
the area into a walk or patio or erect a fence. 

26. Insect Injury — Numerous insects, including grubs, ants, sod webworms, chinch 
bugs, leafhoppers, and others may damage turf. Insect injury may closely re- 
semble one or more lawn diseases. For information concerning lawn insects and 
their control, contact your county agent or extension entomologist. See under Leaf 
Spots (above) . 

27. Mosaic (primarily bluegrass) — Yellowish or light and dark green mottling and 
striping of leaves. Control: None suggested. 

28. Downy Mildew (Bermudagrass) — Southwestern states. Leaf tips have short, black, 
dead areas. Causes little damage. 



272 LAWSON CEDAR 

LAWSON CEDAR -See Juniper 

LAYIA — See Chrysanthemum 

LEADPLANT - See False - indigo 

LEADTREE - See Honeylocust 

LEATHERLEAF - See Blueberry 

LEATHERWOOD, WICOPY (Dirca) 

1. Rust — Eastern half of the United States. Small yellowish spots on the leaves. 
Alternate host is Carex. Control: Destroy the alternate host. If necessary, apply 
ferbam or zineb several times, 10 days apart, starting 1 or 2 weeks before rust 
normally appears. 

2. Sooty Mold — Black moldy blotches on the leaves and twigs. Control: Control in- 
sects with malathion sprays. 

LEBBEK — See Honeylocust 

LEBOCEDRUS-See Juniper 

LEDUM— See Labrador - tea 

LEEK — See Onion 

LEIOPHYLLUM - See Labrador - tea 

LEMAIREOCEREUS - See Cactus 

LEMON -See Citrus 

LEMON MINT -See Salvia 

LEMON - VERBENA - See Lantana 

LENTIL (Lens; -See Pea 

LEONOTIS-See Salvia 

LEOPARDSBANE — See Chrysanthemum 

LEPIDIUM-See Cabbage 

LETTUCE [COS, HEAD, LEAF, ROMAINE ], CELTUCE (Laruca^; 

ENDIVE, ESCAROLE, CHICORY (Cichorium); CARDOON, ARTICHOKE or 

GLOBE ARTICHOKE (Cynara); JERUSALEM -ARTICHOKE (Helianthus); 

BLACK -SALSIFY (Scorzonera;,- SALSIFY, VEGETABLE OYSTER (Tragopogon; 

1. Bottom Rots, Drop, Head or Tuber Rots, Southern Blight, Stem or Crown Rot 
(celtuce, chicory, endive, escarole, Jerusalem-artichoke, lettuce) — General arid 
destructive. Head wilts and rots. Often starts with the lowermost leaves. May be- 
come slimy and foul-smelling, or covered with a dense, white, gray or blue-green 
mold growth. Upright lettuce varieties are often less seriously damaged. Jerusalem- 
artichoke varieties differ in resistance. Heads or tubers continue to rot after harvest. 
Control: Avoid overwatering and overcrowding. Do not plant in wet, poorly 
drained soil. Keep down weeds. Three- or 4-year rotation. Harvest and refrigerate 
promptly. Store only sound, disease-free heads or tubers. Destroy crop refuse after 
harvest. Plow cleanly and deeply. Polyethylene mulches under the plants in strips 



LETTUCE 273 



will largely prevent head rots. Or apply Terraclor as a spray or dust to head let- 
tuce only, just before thinning (plants 2 to 3 inches tall) . Repeat 10 days later. 
Follow the manufacturer's directions. Wet the lower leaves and soil under the 
plants. Control insects with malathion sprays. Grow upright lettuce varieties 
and types (e.g., Romaine or Cos, Iceberg) . Treat seedbed soil as for Seed Rot (be- 
low) . 

2. Tipburn — General and destructive, especially on summer and indoor lettuce 
crops. Most severe on head lettuce during hot, humid periods. Margins of tender 
leaves turn brown to black and dry. Slimy soft rots may follow. Control: Plant in 
well-drained soil. Cultivate deeply and frequently to avoid soil packing. Use 
fertilizers sparingly. Grow tolerant lettuce varieties: Alaska, Arizona Sunbright, 
Blackpool, Climax, Cornell 456, Cosberg, Golden State C and D, Great Lakes 
118, 366, and 659, Great Lakes Emerald, Imperial 44, 410 and 456, Jade, New York 
515 and PW55, Pennlake, Premier Great Lakes, Progress, Resistant Grand Rapids, 
Ruby, Salad Bowl, Sunblest No. 1, Sweetheart, and Vanguard. 

3. Aster Yellows, White Heart, Curly Dwarf — Widespread. Center leaves become 
dwarfed, twisted, and yellowed. Lettuce heads are loose and lightweight — or may 
not even form. Plants dwarfed, "bunchy," and yellowish. May die prematurely. 
Control: Keep down weeds in and around the garden. Destroy the first infected 
plants. Plant at the time recommended for your area. Control leafhoppers which 
transmit the virus. Apply methoxychlor and malathion at about 5-day intervals. 

4. Mosaics (primarily lettuce) — General. Leaves mottled yellow and light green, 
ruffled, or even distorted and dwarfed. Older plants are stunted, dull green to yellow 
or brown. May die or not. May not form a head. Symptoms are often masked in 
hot weather. Control: Plant indexed, mosaic-free lettuce seed. Destroy young, in- 
fected plants when first seen. Keep down weeds. Destroy plant refuse after har- 
vest. Rotate. Control aphids with malathion. Apply at 3- to 5-day intervals. Tolerant 
lettuce variety: Parris Island Cos. 

5. Doiuny Mildew (artichoke, celtuce, chicory, endive, escarole, Jerusalem-artichoke, 
lettuce, spinach) — General during cool (43° to 53° F.) , humid weather. Pale green 
or yellowish areas develop on the upper leaf surface. A fluffy, whitish to bluish-gray 
mold may form on the corresponding underleaf surface during cool, damp weather. 
Later the spots turn brown. When severe, plants may be dwarfed and yellow with 
the outer leaves turning brown and dying. See Figure 20B and D under General 
Diseases. Control: Plant disease-free seed grown in the western states. In the seed- 
bed, increase air circulation and light. Avoid overcrowding, overwatering, overferti- 
lizing, and water splashing on the leaves. Rotate. Collect and burn plant debris 
after harvest. Do not work among wet plants. Plant in well-drained soil where air 
circulation is good. The seedbed soil should be treated with heat or chemicals be- 
fore planting (pages 437-44) . Apply maneb or zineb at 5- to 7-day intervals in damp 
weather, especially in the seedbed. Keep down the humidity. Normally resistant 
lettuce varieties, where adapted: Arctic King, Bath Cos, Big Boston, Grand Rapids, 
Imperial [strains D, 44, 152, 410, 615, 847, 850], Salad Bowl, and Valverde. Keep 
down weeds. 

6. Fusarium Yellows, Wilt (lettuce) — Leaves turn yellow, wilt, and drop starting 
at the base of the plant. Dark brown streaks inside stems and larger veins. Control: 
Long rotation. Plant in well-drained soil. 

7. Gray-mold Blight — General in lettuce hot beds and indoors in damp weather. 
Grayish-green or brownish water-soaked areas on the lower leaves, stem or flower 
head (buds) of globe artichoke. May be covered with a coarse gray mold in damp 
weather. Plants may collapse. Heads may rot in the field or after cutting. Seed- 
lings may wilt and collapse. Control: Treat in the seedbed as for Downy Mildew 



274 LETTUCE 

(above) and Seed Rot (below) . If necessary, dust or spray with mixture of Terra- 
clor and captan. Follow the manufacturer's directions. Indoors, keep water off 
the foliage and increase air circulation. Store heads as cool and dry as practical. 

8. Lettuce Big Vein (lettuce) — Widespread. Most severe in cool seasons. Plants may 
be stunted with crinkled, yellowed, and brittle leaves. Leaf veins are swollen and 
light yellow in color. Yellow spots may develop in young leaves with irregular, 
brown blotches on the older leaves. Heads may not form or are reduced in size 
and delayed in maturity. The big vein fungus can carry tobacco necrosis virus to 
healthy plants. Control: Plant in clean or sterilized soil (pages 437-44) which is 
well-drained. Keep the soil on the dry side. Grow transplants at a temperature of 
75° F. or above, or plant outdoor lettuce as a midsummer or fall crop. Treating the 
soil with Terraclor as for Seed Rot (below) and Bottom Rot (above) may be bene- 
ficial. Resistant varieties: Caravan and Forty-niner. 

9. Bacterial Leaf Spots and Rots, Bacterial Wilt, Marginal Blight (chicory, endive, 
Jerusalem-artichoke, lettuce) — Widespread in wet weather. Leaf margins may rot 
and turn a brownish-black and later become thin and brittle. Small, water-soaked, 
yellow to yellowish-red, brown, or black spots or large, irregular blotches may 
develop in the leaves. Spots may remain small and dry or enlarge and become 
soft and moist. Leaves and stems may wilt and rot. Plants may be yellowed and 
stunted. Control: Same as for Downy Mildew (above) . Avoid splashing soil on 
plants when watering. Control insects by using methoxychlor and malathion sprays. 

10. Seed Rot, Damping-off — General. Seeds rot. Stand is poor. Seedlings wilt and col- 
lapse from a rot at the soil line. Roots are brown and rotted. Control: In the seed- 
bed, mix a combination of Terraclor 20 per cent dust and captan 7i/ 2 per cent dust 
into the top 4 inches of soil. Use i/ 2 cup of each mixed (rototilled) into 100 square 
feet of bed. Or apply a drench of Terraclor 75 per cent and captan 50 per cent 

(0.8 ounce of each in 10 gallons of water to 200 square feet of seedbed) . Other- 
wise treat as for Downy Mildew (above) . If stand has been poor, dust lettuce 
seed with chloranil, thiram, captan, or Semesan. Dust chicory, endive, escarole, and 
salsify seed with thiram or Semesan. 

11. Rusts — Small, bright yellow to yellow-orange spots on the leaves. Pustules may later 
be reddish-brown and powdery. Leaves may wither. Control: Same as for Downy 
Mildew (above) . Alternate hosts: sedges (Carex spp.) , or none. Destroy all sedges 
within 100 yards of the garden area, where practical. 

12. Powdery Mildew — General. Primarily a lettuce problem on the West Coast. Small 
to large patches of whitish mildew on leaves. May cover the foliage in overcast, 
damp weather. Leaves later curl and turn yellow, then brown and die. Control: 
In problem areas, plant resistant lettuce varieties: Arctic King, Bath Cos, Big Bos- 
ton, Imperial strains, and Salad Bowl. Several sulfur dusts or sprays, 10 days apart, 
should keep mildew in check. Apply as necessary. 

13. Root Rots, Stunt, Wilt — Lower leaves a dull, dark green. Later wilt, wither, and 
die. Plants stunted with poor heads. Inside of roots is brown or black. Roots are 
rotted. Seedlings wilt and collapse. Often associated with nematodes. Control: Avoid 
planting in heavy, cold, wet soil. Rotate. Fertilize and water plants to maintain 
vigor. Avoid fertilizers high in ammonia or nitrite. Resistant lettuce varieties and 
types: Big Boston, Grand Rapids, Cos, Simpsons Curled, and White Boston. Control 
insects by malathion sprays. 

14. Other Fungus Leaf Spots or Blights, Anthracnose — Spots of various sizes and 
colors which may enlarge and run together, forming irregular blotches. Spots may 
drop out leaving shot-holes. Leaves may wither and die starting usually with the 
oldest ones. Plants may appear sickly and stunted. Control: Same as for Downy 



LILAC 275 

Mildew (above) . Spray weekly in the field during rainy periods using zineb, 
maneb, or fixed copper. Keep plants growing vigorously. Plant disease-free seed 
or treat as for Seed Rot (above) . Collect and burn plant debris after harvest. 
Lettuce varieties differ in resistance. 

15. Lettuce Brown Blight — Pale yellow or brown, irregular spots and blotches develop 
on the inner leaves. Spots later enlarge. Plants become stunted, flat, and rosette- 
like. The leaves on such plants gradually turn brown starting at the base. Many 
plants die before harvest. Control: Plant resistant varieties: Imperial and Great 
Lakes strains, or Big Boston. 

16. Root-knot — General over much of the United States. See under Bean, and (37) 
Root-knot under General Diseases. 

17. Slime Molds — See under Lawngrass. Control measures are not needed. 

18. Spotted Wilt — Irregular, brown, dead spots in the inner leaves. Outer leaves droop 
and are stunted. Leaves may twist causing the head to lean one way. Leaves and 
entire plant may show a general yellowing. Plants often die early. Control: Same as 
for Mosaics (above) . Control thrips which transmit the virus. Use malathion. 

19. Curly-top (lettuce) —See (19) Curly-top under General Diseases. 

20. White-rust (primarily salsify and black-salsify) — General. Often destructive in 
warm, moist weather. Foliage is twisted and distorted. Numerous whitish pustules, 
which yellow with age, break out on all aboveground plant parts. Control: Rotate. 
Keep down goatsbeard and other related weeds. Pick off and burn spotted leaves. 
Spraying as for Downy Mildew (above) should be beneficial. 

21. Leaf and Stem Nematode (salsify) —See (20) Leaf Nematode under General 
Diseases. 

22. Verticillium Wilt — See (15B) Verticillium Wilt under General Diseases. 

23. Crown Gall (Jerusalem-artichoke, lettuce) — See (30) Crown Gall under General 
Diseases. 

24. Scab (salsify) —See (14) Scab under General Diseases. 

25. Other Root-feeding Nematodes (e.g., lance, naccobus, pin, reniform, root-lesion, 
spiral, sting, stubby-root, stylet or stunt) — Associated with stunted, sickly plants. 
Roots often short, stubby, bushy, and discolored. Control: Same as for Root-knot 
(above) . 

LEUCAENA - See Koneylocust 

LEUCOJUM-See Daffodil 

LEUCOPHYLLUM - See Texas Silver Leaf 

LEUCOTHOE - See Labrador - tea 

LIATRIS — See Chrysanthemum 

LIBOCEDRUS-See Juniper 

LIGUSTRUM - See Privet 

LILAC [AMUR or MANCHURIAN, CHENGTU, CHINESE, COMMON or 
OLD-FASHIONED, EVANGELINE, HIMALAYAN, HUNGARIAN, 
HYBRID, JAPANESE, JAPANESE TREE, KOREAN EARLY, LITTLE 

LEAF, NODDING, PEKING, PERSIAN, PINK PEARL, ROUEN ] (Syringa) 

1. Powdery Mildew — General but not serious. Grayish-white mold patches or coating 
on the leaves from midsummer on. Most common on the lower or shaded leaves. 



276 LILAC 

See Figure 21C under General Diseases. Control: Apply Karathane, sulfur, or Acti- 
dione several times, 10 days apart, starting when mildew is first seen. 

2. Shoot Blights, Dieback, Stem and Twig Cankers — Common and severe in wet 
spring weather where plants are shaded or crowded. Leaves turn a blackish-brown 
and cling to the stem or drop early. Flower buds or blossoms wilt and turn brown 
to black. Dark brown to black, elongated cankers on the stem. Shoots wilt and may 
die back to the ground. Often associated with stem borers. Control: Prune shrubs 
annually for good air circulation. Avoid overcrowding. Prune out and burn 
blighted portions when found. Swab pruning tools with 70 per cent denatured 
alcohol between cuts. Apply zineb, maneb, fixed copper, or bordeaux mixture 

(4-4-50) before spring wet periods starting as the leaves begin to unfold. Spray 
after bloom as for Leaf Spots (below) . Avoid overfertilizing with manure or a 
high-nitrogenous fertilizer and planting close to rhododendron and privet. Spray 
with dieldrin to control borers. Check with your county agent or extension entomol- 
ogist regarding timing of sprays for your area. 

3. Leaf Spots, Leaf Blotch or Blights, Anthracnose — Small to large, variously colored 
spots, often with dark margins. Spots may later drop out leaving irregular ragged 
holes. Control: If serious enough, apply zineb, maneb, captan, or fixed copper 
several times, 7 to 10 days apart. Start just after lilacs have bloomed. Applications 
may also be needed before summer and fall rainy periods in wet seasons. 

4. Gray-mold Blight, Botrytis Blight, Blossom Blight — Buds and blossoms may turn 
light brown and water-soaked, rot, and become covered with a coarse, tannish-gray 
mold. Common in humid, wet areas. May follow frost or other injury. Control: 
Same as for Shoot Blights and Leaf Spots (both above) . 

5. Root Rots — Certain branches, or the entire shrub may die. Underground parts are 
rotted. See under Apple. May be associated with root-feeding nematodes (e.g., 
citrus, dagger, lance, root-lesion, spiral, stem, stylet or stunt) . Control: Carefully 
dig up and burn affected plants, including as many of the roots as possible. Do not 
replant in the same soil without first drenching the soil as for Verticillium Wilt 
(below) . 

6. Wood Rot — See under Birch, and (23) Wood Rot under General Diseases. Com- 
monly follows borers and other types of injuries. 

7. Mosaic — Virus complex. Leaves are dwarfed, puckered, folded, and mottled or 
spotted with yellow. May closely resemble Graft Blight (below) and a soil defi- 
ciency. Symptoms tend to disappear during certain seasons. Control: Dig up and 
destroy infected plants when found to be mosaic. 

8. Ringspot — Pale green to yellow rings, spots, lines, and broad bands on the leaves. 
Leaves may be distorted and ragged with holes. Control: Same as for Mosaic 
(above) . 

9. Witches' -broom — On common lilac the leaf veins are first yellow and clear. Several 
months to a year later, numerous, slender, lateral shoots with dwarfed leaves are 
formed producing a witches'-broom. On Japanese lilac several (2 to 6) slender 
shoots, usually near the top of the plant, branch freely and bear dwarfed leaves 
which are often twisted and rolled. Control: Same as for Mosaic (above) . 

10. Verticillium Wilt — Leaves on one or more stems are pale, wilt, and fall early start- 
ing at the base and spreading upward. Clusters of leaves at the stem tip may re- 
main hanging for a long time. Stems show brownish-green streaks under the bark. 
Branches die back. Slightly infected shoots are stunted and thickened with stunted 
flower clusters. Control: Dig up and burn infected plants, roots and all. Avoid 
planting in the same location for 5 or 6 years without first drenching the soil with 
Vapam or V.P.M. Soil Fumigant following the manufacturer's directions. 



LILY 277 



Fig. 140. Graft incom- 
patibility of lilac. (Iowa 
State University photo) 




11. Graft Blight, Incompatibility Disease — Occurs where lilac is grafted on privet. 
Leaves are dwarfed, irregular, rolled, curled, or cupped. Leaves are usually yellow- 
ish, later brown, at the margins and between the veins. Plants are stunted. Re- 
sembles a nutrient deficiency or Mosaic. See Figure 140. Control: Propagate lilac 
on its own roots or use a piece root-graft. Check with your local nurseryman if you 
are propagating lilacs. 

12. Frost Injury — Freezing temperatures in late spring may cause the leaves to become 
torn along the veins in an irregular pattern. 

13. Root-knot — See under Peach, and (37) Root-knot under General Diseases. 

14. Crown Gall — See (30) Crown Gall under General Diseases. 

LILY [BERMUDA, CANDLESTICK, EASTER, GOLDENBANDED, HANSON, 
JAPANESE EASTER, MADONNA, MARTAGON, MICHIGAN, REGAL or 
ROYAL, SHOWY, TIGER, TURKS-CAP, WILD (ORANGE-RED or WOOD), 

WILD YELLOW or CANADA], also Lilium Columbian, L. formosanum, L. 
henryi, L. hollandicum, L. humboldtii, L. japonkum, L. pardalinum, L. 

rubrum, L. tenuifolium, L. testaceum, and L washingtonianum (Lilium); 

LILY -OF -THE -VALLEY (Conva//aria; ; BELLWORT, MERRYBELLS (Uvularia) 

l.Botrytis Blights, Gray-mold Blight, Stem Rot — General and serious on most lilies 
in damp weather. Symptoms variable. Yellowish to reddish-brown or dark brown 
(sometimes light gray) , oval to round spots on the leaves, stems, and flowers. Spots 
may enlarge and run together, blighting the whole leaf. Leaves may blacken, wither, 
and hang limply, often starting at the base of the stem. The tip of the shoot or the 
entire top may die and bend sharply downward. Bulb or rhizome may rot. Plants 
often stunted. Buds rot or open to distorted, brown-flecked flowers. A coarse gray 
mold may grow on affected parts in damp weather. See Figure 19C under General 
Diseases. Control: Carefully collect and destroy infected parts as they occur. 
Burn tops in the fall. Space plants. Increase air circulation. Keep down weeds. 
Plant best quality, disease-free bulbs (or rhizomes) in a sunny spot in well-drained 
soil. Avoid splashing water on the foliage when watering. Avoid overfertilizing 
with nitrogen. During cool, wet weather apply 4-2-50 bordeaux mixture (4 ounces 
of copper sulfate and 2 ounces hydrated spray lime in 3 gallons of water) at 7- to 
10-day intervals. Add detergent or spreader-sticker to ensure wetting of the foliage. 
Cover all aboveground parts with each spray. Regal, Hanson, Martagon, and 



278 LILY 

Goldenbanded lilies are usually much more resistant than Madonna, Showy, Tiger, 
and Easter. Indoors, increase light and circulation. Lower the humidity. Spray 
buds and early blooms lightly with zineb. Keep water off the foliage. 

2. Bulb Rots, Scale Rots, Root Rots — Cosmopolitan and serious. Plants stunted and 
sickly with rotted bulb and roots. Foliage turns yellow or purple. Stems may dry 
up from the base with leaves withering and falling. Flowers may be blasted and 
fewer in number. Often associated with viruses, nematodes, and mites. Mold 
growth on stored bulbs. Bulbs may be wet, slimy, and foul-smelling, soft or dry and 
punky or "chalky." Marginal, brown areas may develop on certain leaves as they 
get older. Lily bulb scales may show discolored "scabby" spots. Bulbs are unsightly. 
See Figure 49C under General Diseases. Control: Plant large, highest quality bulbs 
or rhizomes in open, well-drained soil, sterilized if practical. Before planting, soak 
lily bulbs 30 minutes in a mixture of Terraclor 75 (1 ounce in 6 gallons of water) 
and captan 50 or ferbam 76 (2 ounces in 6 gallons) . Dig up and destroy all infected 
plants and surrounding soil. Avoid wounding bulbs or growing plants. Five- to 
6-year rotation. Avoid overwatering. Practice balanced soil fertility based on a soil 
test. Mixing Terraclor into the furrow before planting has proved beneficial. 
Follow the manufacturer's directions. Keep bulbs cool in storage. 

3. Mosaics, Mottle, Flower Breaking — Serious and widespread on lilies. Symptoms 
variable. Leaves mottled, yellow, and light and dark green or with yellowish (or 
brown) streaks. Leaves may be stunted, curled, twisted, and narrowed. Flowers 
are often blotched or "broken." Some species are stunted or killed; die from root 
and bulb rots. Symptoms may fade as plants get older. Certain lilies carry the 
viruses but show no symptoms. Often confused with various mineral deficiencies, 
but symptoms are usually more uniform. See Figure 141. Control: Destroy infected 
plants when first seen as they will not recover. Plant only the largest, virus-free 
bulbs from a reputable nursery, or grow from seed. Control aphids which transmit 
the viruses. Use lindane or malathion. Keep down weeds. Resistant lily species: 
Hanson and Lilium pardalinum. Avoid growing L. formosanum and L. rubrum 
near other lilies or near "broken" or mosaic-infected tulips. Grow Goldenbanded 
and L. rubrum lilies separately. Grow L. henryi from seed. 

4. Rosette, Yellow Flat — Very destructive. Lily plants may be dwarfed. The upper 
leaves pale green or yellowish and tightly curled downward forming a basal "ro- 
sette." Leaves are sometimes twisted sideways and are distorted. Often confused 
with frost injury, water-logged soil, aphids, or root and bulb rots. Bulbs progres- 
sively grow smaller each year. Plants rarely flower and never recover. Control: 
Same as for Mosaics (above) . 

5. Fleck (lily) - Plants stunted, distorted, and short-lived. Blocklike, "translucent 
windows" or white, yellowish or brown flecks in leaves. Leaves tend to curl and 
twist. Flower;, are fewer in number and short-lived. May be twisted and streaked. 
Control: Same as for Mosaics (above) . 

6. Ringspot (Easter, regal, and tiger lilies) — Dark, ringlike patterns on leaves which 
soon become dead areas which spread throughout the plant. No flowers are pro- 
duced. Plants twisted and stunted or killed outright. Hybrid lilies may show only 
a faint mottling. Control: Same as for Mosaics (above) . 

7. Noninfectious Chlorosis — Plants stunted. Yellowish leaves with green veins. May 
closely resemble the Mosaic complex except the yellowish patterns are more regu- 
lar and more yellow. Control: Common in alkaline soils. Have the soil tested. Add 
acid fertilizer and a solution of ferrous sulfate to the soil. For fast results, spray 
the foliage with ferbam, iron (ferrous) sulfate, or an iron chelate. 



LILY 



279 



Fig. 141. Lily mosaic. 



m 






Hi w 








H ' TO 

BR-:: - 

; a? ^ 


e - , i*i» ; 


■'"' I 







8. Stem i?ofo or Canker, Foot Rots, Stump Rot, Root Rots — Cosmopolitan. Plants 
often stunted and sickly. May wilt gradually or suddenly, wither, often collapse. 
Stem rots at the ground line. Roots are rotted. Tips of young plants may wither. 
Control: Same as for Bulb Rots. In addition, wash out mud from the crowns as 
plants emerge. Dipping bulbs just before planting in a mixture of Terraclor and 
ferbam or captan may be beneficial. See under Bulb Rots (above) . 

9. Rusts — Widespread. Yellow spots on the upper leaf surface with yellow-orange, 
reddish-brown or black, powdery pustules on the corresponding underleaf surface. 
Alternate hosts: Sporobolus (ribbon or reed grasses) or none. Control: Destroy 
infected leaves when found. Where serious, apply ferbam, zineb, maneb, or dichlone 
at 10-day intervals. Destroy weed hosts. 

10. Stalk Rot, Southern Blight — May be serious in southern states in heavy, wet soils. 
Chalky white rot of bulb with white, fanlike mold patches. Plants wither and die in 
patches. Regal lily is very susceptible. Control: Same as for Bulb Rots (above) . 
Resistant lily varieties: Easter and Showy. 

W.Leaj and Bud (Bulb) Nematode, "Bunchy Top," Dieback (lily) —Pacific North- 
west. Symptoms variable. Leaves may be blotched yellow and green. Leaves then 
turn yellow, bronze to dark brown and curl up against the stem. Affected leaves 
may be thick, pointed, produce a bunchy top or "crooks." Lower leaf whorls 
usually are the most seriously infested. Forced, indoor plants may produce "blind" 



280 LILY LEEK 

buds. Control: Dig up and burn infested plants when first found. Plant disease- 
free, best quality, heat-treated bulbs in clean, well-drained soil. Or soak dormant 
bulbs before planting in a hot formaldehyde solution (1 tablespoon of 37-40 per 
cent commercial formaldehyde in 2 quarts of water) at exactly 111 F. for an hour. 
Then dip in a chloranil solution (5 ounces of wettable Spergon in 3 gallons of 
water) . Dry and plant immediately. Follow a three-year rotation. 

12. Root-lesion (Meadow) and Other Nematodes (e.g., dagger, lance, spiral, stubby-root, 
stylet or stunt) — Plants may be stunted. Foliage turns pale or yellow prematurely. 
Roots stunted and die back. May be bushy, "stubby," or stunted with numerous 
dead spots. Nematodes are often part of a disease complex with root- and bulb- 
rotting fungi and mites. Control: Rotate. Same as for Leaf and Bud Nematode 

(above) . Plant in clean or sterilized soil (pages 437-44) . Root-prune infested roots 
before treating and planting. 

13. Root-knot — See (37) Root-knot under General Diseases. Control: Same as for 
Root-lesion Nematode (above) . 

14. Damping-off — Cosmopolitan. See under Beet. 

15. Leaf Spots, Anthracnose — Spots of various sizes and shapes on the leaves. Spots may 
drop out, leaving ragged holes. Leaves may wither and die early. Spots may also 
occur on leaf and flower stalks. Young plants may be stunted. Control: Same as for 
Rusts (above) . Rotate. 

16. Frost Injury — The growing point is killed and plants are stunted by severe frosts. 
Leaves may be "puffy." Control: Cover young shoots or mulch on cold nights when 
freezing temperatures are expected. 

LILY LEEK -See Onion 

LILY -OF -THE -VALLEY -See Lily 

LIME -See Citrus 

LIMONIUM - See Sea - lavender 

LINARIA — See Snapdragon 

LINDEN [AMERICAN or BASSWOOD, COMMON, COMMON 

EUROPEAN, CRIMEAN, JAPANESE, LARGE-LEAVED, MANCHURIAN, 

MONGOLIAN, PYRAMIDAL, SILVER, SMALL - LEAVED EUROPEAN, 

WEEPING or PENDENT SILVER, WEEPING WHITE (Tilia) 

1. Leaf Blotch or Blight, Anthracnose — General. Leaves develop small to large, round 
to irregular, light brown spots with blackish-brown margins. Spots enlarge and form 
blotches along the veins. Leaves may wither and drop early. Young twigs and 
branches may die back. Control: Prune out and burn dead or cankered twigs. 
Collect and burn fallen leaves. Fertilize trees to increase vigor. Spray as buds start 
to swell. Repeat twice more at 10-day intervals. Use fixed copper, zineb, ferbam, 
captan, or bordeaux mixture (4-4-50) . 

2. Twig Blight, Dieback, Trunk and Branch Cankers — See under Elm and Maple. 

3. Powdery Mildews — General. Powdery, grayish-white mold on leaves and young 
shoots. If severe, leaves may turn yellow and wither. Control: Where serious enough, 
spray twice, 10 days apart, using sulfur or Karathane. Start when mildew is first 
evident. 

4. Leaf Scorch — Margins of leaves turn brown in midsummer following hot, dry, 
windy weather. Control: Water during summer dry periods. Fertilize and prune 
out trees to increase vigor. 



LOBELIA 281 



5. Leaf Spots, Spot Anthracnose — Generally small spots on the leaves. Of various 
colors and shapes. Spots may drop out leaving shot-holes. Control: Same as for Leaf 
Blotch (above) . 

6. Wood Rots — Cosmopolitan. See under Birch, and (23) Wood Rot under General 
Diseases. 

7. Sooty Mold — Black, sooty mold patches on leaves. Mold grows on "honeydew" 
secreted by aphids, scales, and other insects. See Figure 26 under General Diseases. 
Control: Control insects with malathion sprays. 

8. Slime Flux, Wetwood — See under Elm. 

9. V erticillium Wilt — See under Maple and Elm. Streaks in the sapwood are dark 
gray. 

10. Root Rot — See under Apple, and (34) Root Rot under General Diseases. 

11. Sunscald, Winter hi jury — Common on newly planted trees with thin bark. See 
under Elm and Apple. 

12. Bleeding Canker — Northeastern states. See under Beech and Maple. 

13. Mistletoe — See (39) Mistletoe under General Diseases. 

14. Seed Rot, Damping-off — See under Pine. 

LINDERA — See Avocado 

LINGONBERRY-See Blueberry 

LINNAEA — See Twinflower 

UNUM-See Flax 

LIONS -EAR or LIONS - TAIL - See Salvia 

LIPPIA— See Lantana 

LIQUIDAMBAR - See Witch - hazel 

LIRIODENDRON - See Magnolia 

LITHOCARPUS - See Oak 

LITHOSPERMUM - See Mertensia 

LITSEA — See Avocado 

LIVEFOREVER - See Sedum 

LIVERLEAF — See Anemone 

LOBELIA, CARDINALFLOWER, INDIAN - TOBACCO (Lobelia) 

1. Root Rots, Stem and Crown Rot, Damping-off — Lower leaves turn yellow. The 
crown and lower part of the stem decay. The tops wilt and die, or may be stunted. 
Seedlings wilt and collapse. Control: Avoid overwatering, overcrowding, and 
planting in poorly drained soil. Take cuttings only from healthy plants. Root cut- 
tings in a sterile medium (pages 437-44) . Drench crown and surrounding soil with 
a 1:1,000 solution of mercuric chloride when plants are young. 

2. Mosaic — Leaves blotched and mottled pale and dark green (certain varieties) . 
Young leaves are distorted and twisted. Older ones are somewhat malformed and 
brittle. Control: Plant healthy stock. Keep down weeds. Destroy the first infected 
plants. By using lindane or malathion, control aphids which transmit the virus. 



282 LOBLOLLY-BAY 

3. Leaf Spots — Round to irregular, pale tan to reddish-brown spots on the leaves. 
Leaves may wither and drop early. Control: Pick off and burn spotted leaves as they 
appear. Spray with zineb or maneb during wet periods. 

4. Leaf Smut — See (13) White Smut under General Diseases. 

5. Gray-mold Blight — See under Chrysanthemum, and (5) Botrytis Blight under 
General Diseases. 

6. Rust — See under Chrysanthemum, and (8) Rust under General Diseases. 

7. Root-knot and Other Nematodes — See (37) Root-knot under General Diseases. 
Lobelia is very susceptible. 

8. Curly-top — Shoots have rosettes. Flowers are reduced in size. See (19) Curly-top 
under General Diseases. 

9. Spotted Wilt — See under Bellflower, and (17) Spotted Wilt under General 
Diseases. 

LOBLOLLY - BAY - See Franklin - tree 

LOBULARIA-See Cabbage 

LOCUST— See Honeylocust 

LOGANBERRY - See Raspberry 

LOLIUM — See Lawngrass 

LONICERA — See Snowberry 

LOOSESTRIFE — See Lythrum and Primrose 

LOQUAT-See Apple 

LOTUS -See Waterlily 

LOVE - LIES - BLEEDING - See Cockscomb 

LUFFA — See Cucumber 

LUNARIA-See Cabbage 

LUPINE (Lupinus) - See Pea 

LYCASTE-See Orchids 

LYCHNIS -See Carnation 

LYCIUM — See Matrimony - vine 

LYCOPERSICON - See Tomato 

LYCORIS-See Daffodil 

LYONIA-See Blueberry 

LYSIMACHIA - See Primrose 

LYTHRUM, PURPLE and WINGED LOOSESTRIFE (Lythrum); MADEIRA - VINE, 
CLIMBING MIGNONETTE (Boussingaultia) 

1. Leaf Spots — See (1) Fungus Leaf Spot under General Diseases. 

2. Root Rot — See under Chrysanthemum, and (34) Root Rot under General Diseases. 

3. Root-knot — See (37) Root-knot under General Diseases. 



MAGNOLIA 283 



MACLURA — See Osage - orange 
MADEIRA - VINE - See Lythrum 

MADRONE-See Blueberry 

MAGIC LILY -See Daffodil 

MAGNOLIA [ ANISE, FRASER or MOUNTAIN, KOBUS, 

LILY - FLOWERED, OYAMA, PINK STAR, SAUCER, SOUTHERN or BULLBAY, 

STAR, SWEETBAY or LAUREL, UMBRELLA, WHITE - LEAF JAPANESE, 

WILSON, YULAN ], CUCUMBERTREE (Magnolia); TULIPTREE or 

YELLOW - POPLAR (Liriodendron); ANISETREE (Micium) 

1. Leaf Spots, Tar Spot, Spot Anthracnose — Widespread but rarely serious. Small 
spots to large, irregular blotches on the leaves. Of various colors and shapes. In- 
fected leaves may drop early. Control: Gather and burn fallen leaves. If practical, 
spray several times, 10 days apart, starting as the buds break open. Use zineb, 
maneb, fixed copper, or phenyl mercury following the manufacturer's directions. 

2. Wood or Heart Rots — Cosmopolitan. Foliage is thin. Upper branches die back. 
Leaves may appear to have a nutrient deficiency. See under Birch, and (23) Wood 
Rot under General Diseases. Control: See under Birch. 

3. Powdery Mildews — Widespread. Powdery, grayish-white patches on the leaves 
and young shoots. If severe, leaves may turn yellow and wither. Control: Apply 
two sulfur or Karathane sprays, 10 days apart. 

4. Twig Blights, Cankers, Dieback — Tops of trees die back. Sunken, flattened, or dis- 
colored cankers form on the twigs, larger limbs, and trunk. The bark over affected 
areas is often discolored and shows longitudinal cracks. Control: Cut out and burn 
cankered wood on the trunk and larger limbs. Paint with a good tree wound dress- 
ing. Keep trees vigorous by fertilizing and watering. Spraying as for Leaf Spots 
(above) may be beneficial. Varieties differ in susceptibility. 

5. Verticillium Wilt — Leaves on one or more branches commonly droop, roll inward, 
and turn yellow. Leaves on other branches or trees may wilt rapidly and turn brown 
or black. Affected leaves usually drop early. Branches die back; may produce 
dwarfed, sickly leaves the second season. The outer sapwood in the larger branches 
and trunk shows a dark discoloration. Control: See under Maple. 

6. Sooty Mold, Black Mildew — Cosmopolitan. Black moldy patches on the leaves. See 
Figure 26 under General Diseases. Control: Spray with malathion to control aphids, 
scales, and other insects. The addition of a fungicide (see under Leaf Spots above) 
will also be beneficial. 

7. Leaf Yellowing or Scorch — Leaves turn yellow and drop during hot, dry periods 
from midsummer on. Control: Water trees during these periods. Fertilize to keep 
trees vigorous. Keep trees pruned out. 

8. Root-knot — See (37) Root-knot under General Diseases. 

9. Root Rots — See under Apple, and (34) Root Rot under General Diseases. May 
be associated with root-feeding nematodes (e.g., burrowing, dagger, lance, root- 
knot, root-lesion or meadow, spiral, sting, stubby-root, stylet or stunt, trophoty- 
lenchulus) . 

10. Seedling Blight, Cutting Rot — See under Pine. 

11. Thread Blight — Southeastern states. See under Walnut. 

12. Felt Fungus — Gulf states. See under Hackberry. 

13. Algal Leaf Spot, Green Scurf, "Red Rust" — Far south and where damp. Velvety, 
reddish-brown to orange, cushiony patches or greenish-brown spots on the leaves. 
Control: Spray with fixed copper during rainy periods. Improve drainage. 



284 MAHONIA 

MAHONIA-See Barberry 

MAIDENHAIR - TREE - See Ginkgo 

MALACOTHRIX-See Chrysanthemum 

MALANGA-See Calla 

MALEBERRY - See Blueberry 

MALLOW -See Hollyhock 

MALTESE CROSS— See Carnation 

MALUS-See Apple 

MALVA, MALVASTRUM - See Hollyhock 

MAMMILLARIA - See Cactus 

MANFREDA - See Centuryplant 

MANGEL, MANGOLD -See Beet 

MANILAGRASS — See Lawngrass 

MANZANITA-See Blueberry 

MAPLE [AMUR, BIGLEAF, BLACK, COLUMNAR RED, COLUMNAR SUGAR, 

DRUMMOND, FERNLEAF, GOLDEN MOON, HARLEQUIN, HEDGE or 

FIELD, JAPANESE, MANCHURIAN, MOUNTAIN, NIKKO, NORWAY 

(many horticultural varieties), PAPERBARK, OREGON, RED or SCARLET, 

RED LEAF (CRIMSON KING. SCHWEDLER'S), SILVER or SOFT, 

STRIPED or MOOSEWOOD, SUGAR or HARD, SYCAMORE, TATARIAN, 

TRIDENT, VINE], BOXELDER [COMMON, CALIFORNIA] (Acer) 

1 . Anthracnose , Lea] Blights — General in wet springs on sugar, silver, and Japan- 
ese maples and boxelder. Irregular, light to reddish-brown, or purplish-brown, dead 
areas on the leaves. Many along the veins. Areas often enlarge, killing the leaf. 
Leaves often appear scorched as if by frost or hot dry weather. Many infected 
leaves drop in late spring. Twigs may die back. See Figure 17B under General 
Diseases. Control: Collect and burn fallen leaves. Prune out dead twigs and weak 
wood to increase air circulation and promote faster drying. If practical, apply 3 
sprays: the first as buds begin to unfold in the spring and then repeat 10 and 20 
days later. Use phenyl mercury, zineb, dichlone, captan, or ferbam plus spreader- 
sticker. Try to time sprays just before wet periods when infections occur. Fertilize 
and water to stimulate vigorous growth. 

2. Verticillium Wilt, Maple Wilt — Widespread and destructive, especially on silver, 
Norway, and sugar maples. Leaves suddenly discolor and wilt on one or more limbs. 
Often on one side of the tree or in the crown. Leaves die and fall or hang on dead 
branches. Later other limbs wilt and die. Olive-green to brown or bluish-black 
streaks may occur in the sapwood, often at a distance from wilting foliage. Infected 
trees may die within a few weeks or live on for a number of years. See Figure 30C 
under General Diseases. Control: Cut down and burn severely infected trees. 
Where only 1 to 6 limbs show wilt, promptly prune off affected parts. Swab tools 
with 70 per cent denatured alcohol between cuts. Paint wounds promptly with 
a tree wound dressing (page 25) . Fertilize heavily and water trees to stimulate 
vigor. Maples vary in resistance. 

3. Leaf Scorch — Light or dark brown areas on the leaf between the veins or along 



MAPLE 285 

the margin. Foliage appears bronzed, dried, and scorched. Affected leaves may drop 
early. Causes: Late spring frost; hot, dry summer winds; and drought (see Figure 
1) . Control: Water trees during summer droughts. Plant in a location protected 
from drying winter and summer winds and bright, all-day sun (especially sugar, 
red leaf, and harlequin maples) . Fertilize and prune to keep trees growing vigor- 
ously. Plant maples recommended for your area. 

4. Chlorosis — May be caused by several factors, e.g., deficiency of one or more min- 
eral elements (especially iron) or moisture, excessive soil moisture or plant nutri- 
ents, hieh water table, winter injury, gas main leak, or change in the soil level. See 
under "Environmental Factors" in Section 2. 

In alkaline soils, iron chlorosis is characterized by a light yellowish color of the 
leaves between the veins. Leaves may later become dwarfed and ivory-colored. 
Twigs are stunted and die back. Affected plants are quite susceptible to winter 
injury. Control: Determine cause of chlorosis and correct the condition. Check iron 
chlorosis by adding iron citrate or sulfate to one or more pest sprays. Trees and 
shrubs can also be treated by applying a mixture of iron (ferrous) sulfate and 
sulfur or iron chelate [e.g., Versenol (Dow) or Sequestrene (Geigy) ] in a series 
of holes in one or more rings in the soil under the outer ends of the branches (see 
page 19 on how to fertilize trees). Three ounces worked into the soil is usually 
enough for an average-sized shrub. Trees take much more. Follow the fertilizer 
manufacturer's directions. Such mixing can be done when the plants are fertilized. 
Check with your nurseryman, county agent, or extension horticulturist on what 
and how much to use. Gelatin capsules containing iron (ferrous or ferric) citrate, 
phosphate, or tartrate are available in some areas. These can be inserted into 3/£ 
inch diameter holes drilled in the base of the trunk. On larger trees the holes are 
usually drilled \i/ 2 inches deep and about 3 inches apart. This should be done by 
a competent arborist since the holes should be drilled correctly and then sealed 
with cork stoppers. Finally the wounds are painted with tree paint or grafting wax 
to seal out moisture and wood rot organisms. Iron chelates may also be injected 
into trees. Treatment is usually undertaken a few weeks before growth starts in 
the spring. 

5. Twig Blights, Cankers, Dieback — Sunken or flattened, discolored cankers appear 
on the twigs, branches, and even the trunk. Twigs and small branches die back. 
Entire trees may die. Affected bark is often sprinkled with small "pimples" which 
may erupt and show black, reddish-brown or coral-red, cushion-shaped bodies. A 
thick callus sometimes with concentric rings may accompany the canker. Wood 
beneath the cankered bark is discolored. Control: Avoid wounding the bark. Make 
flush pruning cuts (see Figure 9) . Cover promptly with a tree wound dressing 
(page 25) . Water and fertilize to stimulate vigor. Prune out cankers several 
inches below diseased areas and paint over cuts with tree wound dressing. Ex- 
tensive trunk cankers cannot be surgically removed. 

6. Bleeding Canker — Northeastern states. Infects Norway, red, sycamore, and sugar 
maples. Reddish-brown cankers form in the inner bark of the trunk and larger 
branches. The bark becomes sunken and furrowed over the cankers. Light brown 
to reddish-brown fluid ("'blood") oozes out through openings in the outer bark. 
Foliage is often sparse, dwarfed, and yellowish-green. Leaves may wilt and branches 
die back. Control: See under Beech. 

7. Branch and Trunk Cankers — Foliage is thin, dwarfed, and sickly. Branches or en- 
tire trees die back from girdling cankers. Roots may decay. Control: See under 
Apple and Beech. Plant in well-drained, rich soil. Avoid bark injuries. 

8. Wood Rots — Cosmopolitan. See under Birch, and (23) Wood Rot under General 
Diseases. Maples are quite susceptible. 



286 MARANTA 

9. Leaf Spots, Tar Spot — General. Round to irregular, light to reddish-brown, gray, 
yellowish-gray, or shiny, black spots on the leaves. Some leaves may wither and 
drop early. Seldom serious. Control: If practical, same as for Anthracnose (above) . 

10. Root Rots — General. Trees decline in vigor. Foliage is thin and sickly. Leaves 
may turn yellow, wither, and fall early. Trees tend to die back. See under Apple, 
and (34) Root Rot under General Diseases. May be associated with root-feeding 
nematodes (e.g., dagger, lance, pin, ring, root-knot, root-lesion or meadow, sheath, 
spear, spiral, stem, stubby-root, stylet or stunt) . 

11. Crown Gall — Rough, irregular, swollen galls at the base of the trunk or on the 
roots. Trees lack vigor. Make poor growth. Leaves may turn yellow. Control: See 
under Apple, and (30) Crown Gall under General Diseases. 

12. Leaf Blisters — Round to irregular leaf "blisters" which are an ochre-buff to dark 
brown above and a pinkish-buff underneath. Leaves may roll and curl inward, drop 
early. Minor pest. Sugar and black maples are most susceptible. Control: If disease 
has been prevalent in past years, apply a single dormant spray. See under Peach, 
and (10) Leaf Curl under General Diseases. 

13. Slime Flux, Wetwood — See under Elm. 

14. Sooty Mold, Black Mildew — Black mold growth on leaves. Control: Spray with a 
mixture of DDT and malathion to control insects (e.g., aphids and scales) which 
secrete honeydew in which the sooty mold fungi grow. 

15. Sunscald, Winter Injury — Maples are very susceptible. See under Elm and Apple. 

16. Powdery Mildews — Minor pest. See under Birch. 

17. Mistletoe — See (39) Mistletoe under General Diseases. 

18. 2,4-D Injury — Boxelder is very susceptible. See under Grape. 

19. Thread Blight — Southeastern states. See under Walnut. 

20. Felt Fungus — Southern states. See under Hackberry. 

21. Seedling Blight — See under Pine. 

MARANTA -See Rabbit Tracks 

MARBLESEED - See Mertensia 

MARGUERITE, MARIGOLD - See Chrysanthemum 

MARINE - IVY - See Grape 

MARIPOSA LILY, GLOBE -TULIP, GLOBE LILY (Calochortus) 

I. Rust — Western half of the United States. Yellow to dark, powdery pustules on the 
foliage. Control: Cut and burn infected foliage after plants bloom. Apply zineb, 
ferbam, or maneb at 10- to 14-day intervals. 

MARJORANA, MARRUBIUM- See Salvia 

MATRICARIA — See Chrysanthemum 

MATRIMONY - VINE, CHINESE WOLFBERRY (Lycium) 

1. Powdery Mildews — Powdery, white mold patches on the leaves in summer and 
fall. Control: Spray or dust 2 or 3 times, starting when mildew first appears. Use 
sulfur, Kara thane, or Acti-dione at 10-day intervals. Follow the manufacturer's di- 
rections. 

2. Leaf Spots — More or less round, tan, gray, or brown spots on the leaves in rainy 



MENTZELIA 287 

seasons. Control: Pick off and burn infected leaves. If serious enough, spray sev- 
eral times, 10 days apart, using zineb or maneb. 

3. Rusts — Reddish-brown, then black, powdery pustules on the leaves. Control: Not 
usually necessary. Same as for Leaf Spots (above) . 

4. Mosaic — See (16) Mosaic under General Diseases. 

MATTHIOLA - See Cabbage 

MAURANDYA — See Snapdragon 

MAYAPPLE (Podophyllum) 

1. R ust — General and destructive. Large areas of the new leaves in the spring turn 
yellowish in spots and later a chocolate-brown in color. Leaves wither and die 
early. Control: Completely dig up and destroy infected plants. 

2. Leaf Spots, Leaf Blight — Widespread in rainy seasons. Spots of various colors, 
sizes, and shapes develop on the leaves, especially in shady spots. Control: Pick 
off and burn spotted leaves. Where practical, apply several sprays, at about 10-day 
intervals, using zineb, maneb, or fixed copper. 

3. Stem Rot — Base of stem may rot causing the foliage to wilt, wither, and die. 
Control: Plant in well-drained soil. Avoid overwatering and heavy shade. Dusting 
or drenching the soil with Terraclor (PCNB) may be beneficial if applied early 
enough. Follow the manufacturer's directions. 

4. Gray-mold Blight — See (5) Botrytis Blight under General Diseases. Control: Same 
as for Leaf Spots (above) . 

MAYDAY -TREE -See Peach 

MAYFLOWER - See Heath 

MEADOWBEAUTY - See Deergrass 

MEADOWRUE-See Delphinium 

MEADOWSWEET -See Rose and Salvia 

MECONOPSIS - See Poppy 

MEDLAR -See Apple 

MELIA — See Chinaberry 

MELISSA -See Salvia 

MENISPERMUM-See Moonseed 

MENTHA -See Salvia 

MENTZELIA, BLAZING - STAR, PRAIRIE LILY (Mentzelia) 

l.Leaf Spots — Small spots on the leaves, usually with a distinctive border. Centers 
of older spots are sprinkled with black dots. Control: Pick off and destroy infected 
leaves. If practical, spray during wet periods using zineb, maneb, or fixed copper. 

2. Rusts — Small yellow to orange spots on the leaves. Alternate hosts: wild grasses or 
none. Control: Same as for Leaf Spots. 

3. Root and Stem Rots — Plants stunted and sickly. May wilt and collapse from rot- 
ting at the soil line and below. Control: Avoid overwatering and planting in heavy, 
poorly drained soil. Drench or dust the soil with Terraclor before planting. Follow 
the manufacturer's directions. 



288 MENZIESIA 

MENZIES1A - See Blueberry 

MERRYBELLS - See Lily 

MERTENSIA, BLUEBELLS, VIRGINIA COWSLIP (Mertensia); 

ALKANET, BUGLOSS, AFRICAN FORGET-ME-NOT (Anchusa); 

BORAGE (Borago); HOUNDSTONGUE, CHINESE FORGET-ME-NOT 

(Cynoglossum); HELIOTROPE (Heliotropium); PUCCOON, 

GROMWELL (Lithospermum); FORGET-ME-NOT (Myosotis); 

MARBLESEED (Onosmodium) 

1. Gray-mold Blight, Botrytis Blight (forget-me-not, heliotrope, mertensia) —Cosmo- 
politan. Especially under cool, moist conditions. Base of stem turns brown, rots, 
and plant may collapse in damp weather. Flowers, leaves, buds, and shoot tips may 
also be blighted. Affected parts may be covered with a coarse gray mold. Control: 
Carefully collect and burn infected plant parts. Space plants. Keep down weeds. 
Spray at 5- to 10-day intervals during cool, moist weather. Use captan, zineb, 
maneb, or fixed copper. 

2. Stem Rots, Crown Rot, Southern Blight, Wilt, Damping-off — Plants wilt and later 
turn brown from rot at the soil line. Affected area may be covered with a dense 
cottony mold. Seedlings wilt and collapse. Control: Remove and destroy infected 
plants together with 6 inches of surrounding soil. Avoid overwatering. Rotate. See 
also under Delphinium. 

3. Downy Mildew (forget-me-not, houndstongue, mertensia) — Pale spots or yellow- 
ish blotches on the upper leaf surface with a delicate, grayish-white mold develop- 
ing on the corresponding underleaf surface in humid weather. Control: Spray at 
5- to 10-day intervals during cool, rainy weather, using zineb, maneb, or fixed 
copper. 

4. Aster Yellows, Curly-top (anchusa, forget-me-not) —See (18) Yellows, and (19) 
Curly-top under General Diseases. 

5. Powdery Mildew (anchusa, houndstongue, lithospermum, mertensia) — White, 
powdery blotches on the stems and leaves. Leaves may turn yellow and wither. 
Control: Space plants. Increase air circulation. Dust or spray with sulfur or Kara- 
thane. 

6. Leaf Spots — See under Chrysanthemum, and (1) Fungus Leaf Spot under General 
Diseases. 

7. Leaf Smut (mertensia) — Round, pale spots or "blisters" on the leaves which are 
later filled with black powdery masses. Control: See (13) White Smut under Gen- 
eral Diseases. 

8. Root-knot — See (37) Root-knot under General Diseases. 

9. Rusts (anchusa, forget-me-not, heliotrope, lithospermum, marbleseed, mertensia) 
— See (8) Rust under General Diseases. Alternate hosts include wild grasses and rye. 

10. Black Ringspot (forget-me-not) —See under Cabbage. 

11. Mosaic (anchusa, mertensia) —Widespread. Mottled, yellowish-green and dark 
green leaves. Plants may be stunted. Control: Dig up and burn infected plants. 
Keep down weeds. Spray with malathion or lindane to control aphids. 

12. Root Rot — See under Geranium, and (34) Root Rot under General Diseases. 

13. Verticillium Wilt (heliotrope) —Leaves and flowers turn black, wilt, and shrivel. 
Brown streaks develop inside stems and appear when stem is cut. Control: See 
(15B) Verticillium Wilt under General Diseases. 

14. Leaf Scorch (heliotrope) — Margins of leaves turn dark brown during hot, dry 
weather. Control: Plant in partial shade in a protected location. Lower the tem- 
perature, if possible. 



MOCK-STRAWBERRY 289 



MESCALBEAN - See Honeylocust 

MESEMBRYANTHEMUM - See Iceplant 

MESPILUS-See Apple 

MEXICAN FIRE - PLANT - See Poinsettia 

MEZEREUM-See Daphne 

MICHAELMAS DAISY - See Chrysanthemum 

MICROMERIA - See Salvia 

MIGNONETTE (Reseda) 

1. Leaf Spot, Blight — Widespread in the eastern half of the United States. Numerous 
small, pale tan to yellowish-brown spots with reddish-brown borders, mostly on 
the lower leaves. Spots enlarge and quickly run together in wet weather. Entire 
leaves become blighted, reddish, and die. Stalks and seedpods may also be in- 
fected. Control: Plant disease-free seed. Spray weekly in rainy weather using zineb. 
maneb, or fixed copper. 

2. Root Rot, Damping-off — Seedlings wilt and collapse. Older plants are stunted 
and sickly with yellowish leaves. Base of stem and roots decay. Control: Destroy 
infected plants. Rotate. Avoid overwatering and planting in poorly drained soil. 
Where practical, replant in sterilized soil (pages 457-44) . 

3. Downy Mildew — Pale spots on the upper leaf surface with a delicate whitish 
mold growing from the corresponding undersurface in moist weather. Control: 
Same as for Leaf Spot (above) . 

4. Root-knot — See (37) Root-knot under General Diseases. 

5. Verticillium Wilt — See (15B) Verticillium Wilt under General Diseases. 

6. Black Ringspot — See under Cabbage. 

7. Yellows — See (18) Yellows under General Diseases. 

MILTONIA-See Orchids 

MIMOSA -See Pea 

"MIMOSA" TREE -See Honeylocust 

MIMULUS — See Snapdragon 

MINNIE -BUSH -See Blueberry 

MINT -See Salvia 

MIRABILIS - See Four - o'clock 

MISSOURI PRIMROSE -See Evening - primrose 

MISTFLOWER — See Chrysanthemum 

MITCHELLA - See Buttonbush 

MITREWORT (Mitella) - See Hydrangea 

MOCK -CUCUMBER -See Cucumber 

MOCKORANGE - See Hydrangea 

MOCK -STRAWBERRY -See Rose 



290 MOLUCELLA 

MOLUCELLA - See Salvia 

MOMORDICA — See Cucumber 

MONARDA, MONARDELLA - See Salvia 

MONEYWORT -See Primrose 

MONKEYFLOWER-See Snapdragon 

MONKEYPUZZLE TREE - See Araucaria 

MONKSHOOD -See Delphinium 

MONKSHOOD -VINE -See Grape 

MONSTERA-See Calla 

MONTBRETIA - See Gladiolus 

MOONFLOWER - See Morning - glory 

MOONSEED (Menispermum); CAROLINA MOONSEED (Cocculus) 

1. Leaf Spo ts — Widespread. Spots of various colors, sizes, and shapes on the leaves. 
Similar spots may also occur on the stems. Control: Pick off and burn spotted 
leaves. If severe, spray several times during rainy periods, at 7- to 10-day inter- 
vals. Use zineb, maneb, or captan. 

2. Powdery Mildew (menispermum) — Widespread. Grayish-white, powdery mold 
growth on the foliage. Control: If serious enough, spray two or three times, 10 
days apart, with sulfur or Karathane. 

3. Leaf Smut (menispermum) —See (13) White Smut under General Diseases. 

4. Root Rot — See (34) Root Rot under General Diseases. 

5. Burrowing Nematode — Florida. Associated with sickly, declining Carolina moon- 
seed plants. Control: Set disease-free plants in sterilized soil. 

MORNING-GLORY [BUSH, COMMON, IVYLEAF, WHITE- EDGE], HEARTS 

AND HONEY VINE, GIANT NIGHT WHITE BLOOMER (Ipomoea); 

ARGYREIA; MOONFLOWER (Calonyction); CALIFORNIA - ROSE, BUSH 

MORNING-GLORY, BINDWEED (Convolvulus); JACQUEMONTIA; 

CYPRESSVINE, STARGLORY, CARDINAL CLIMBER (Quamoclit) 

1. Leaf Spots — Spots of various colors and sizes on leaves, often with a distinct mar- 
gin. Control: Pick off and burn spotted leaves. Cut and burn tops in the fall. If 
serious enough, spray as for Rusts (below) . 

2. Rusts — Primarily in the southern states. Unimportant in gardens. Yellowish spots 
on the upper leaf surface and reddish-brown, powdery pustules on the underleaf 
surface. Alternate hosts include pines. Control: Apply ferbam, fixed copper, or 
zineb several times, 10 days apart. 

3. White-rust — Widespread. Serious sometimes in the southern states. See under Cab- 
bage, and (9) White-rust under General Diseases. 

4. Stem Rot, Stem Canker, Damping-off — Sunken brown areas on the stem or soft 
rotting of the crown which may be covered with a cottony mold. Seedlings wilt 
and collapse. Control: Destroy infected plants. Plant in clean, well-drained soil. 
Avoid overwatering. 



MULBERRY 291 



5. Root Rot — See (34) Root Rot under General Diseases. May be associated with 
root-feeding nematodes (e.g., reniform, sting) . 

6. Root-knot — See (37) Root-knot under General Diseases. 

7. Leaf Nematode (moonflower) — Brown blotches on the leaves, bounded by the 
veins. Leaves may shrivel, die, and hang on the plant. Variegated moonflower va- 
rieties are considered more susceptible. Control: See under Chrysanthemum, and 
(20) Leaf Nematode under General Diseases. 

8. Mosaic — Yellowish-white and greenish mottling of the leaves. See (16) Mosaic 
under General Diseases. 

9. Curly-top — Western states. See (19) Curly-top under General Diseases. 

10. Fusarium Wilt (morning-glory) —See (15A) Fusarium Wilt under General Dis- 
eases. 

11. Blossom Blight — See (31) Flower Blight under General Diseases. 

12. Thread Blight (jacquemontia, morning-glory) — Southeastern states. See under 
Walnut. Control: Spray as for Leaf Spots (above) . 

MORUS-See Mulberry 

MOSES- IN -A- BOAT- See Rhoea 

MOSQUITO BILLS- See Primrose 

MOSS - PINK - See Phlox 

MOTHER -OF -THYME -See Salvia 

MOUNDLILY-See Yucca 

MOUNTAIN - ASH - See Apple 

MOUNTAIN - BLUET - See Chrysanthemum 

MOUNTAIN CRANBERRY - See Blueberry 

MOUNTAIN - HOLLY - See Holly 

MOUNTAIN - LAUREL - See Blueberry 

MOUNTAIN - MINT - See Salvia 

MOUNTAIN-SPICEWOOD - See Calycanthus 

MOUNTAIN SPURGE -See Pachysandra 

MUGWORT — See Chrysanthemum 

MULBERRY [ RED, RUSSIAN, WEEPING, WHITE or CHINESE ] (Morus) 

1. Twig Blights, Cankers, Dieback — Widespread. Small to long, sunken cankers on 
the twigs and branches. Branches die back and trees may gradually die over a 
period of years. Small, coral-pink to black "pimples" may be evident in the bark. 
Control: Prune out and burn all twigs and branches showing cankers. Keep trees 
growing vigorously by fertilizing and watering. Varieties differ in resistance. 

2. Bacterial Spot, Blight — General. Small, angular, water-soaked spots on the leaves 
and shoots which turn brown to black and become sunken. Young leaves may be 
distorted and turn yellow to brown. Elongated black spots or stripes on the shoots. 
Twigs may be blighted. Trees may be stunted. Control: Prune out and burn 
blighted twigs in late fall. If practical, apply a copper fungicide before rainy peri- 
ods. Avoid overhead sprinkling in the nursery. 



292 MULLEIN-PINK 

3. Fungus Leaf Spots — Common in rainy seasons, but cause little damage. Spots of 
various colors, sizes, and shapes on the leaves. Some leaves may drop early. Control: 
Collect and burn fallen leaves. If practical, spray several times, 10 days apart, us- 
ing zineb, maneb, or fixed copper. 

4. Powdery Mildews — Powdery, white blotches on the underleaf surface. Control: 
Spray two or three times, 10 days apart, using sulfur or Karathane. 

5. Wood and Heart Rots — See (23) Wood Rot under General Diseases. 

6. False Mildew — Southern states. Indefinite, whitish, cobwebby blotches on the un- 
derleaf surface in midsummer. Yellowish areas later develop on the upper side. 
Leaves may wither and fall early. Most serious in shady areas. Control: Same as 
for Fungus Leaf Spots (above) . 

7. Root-knot — Mulberry is very susceptible. See under Peach, and (37) Root-knot 
under General Diseases. 

8. "Popcorn" (Berry-hardening) Disease — Minor disease in southern states. Carpels 
of fruit are small and remain green, interfering with normal ripening. Control: 
None necessary. 

9. Root Rots — See under Apple, and (34) Root Rot under General Diseases. 

10. Hairy Root — See under Apple. 

11. Rust — Southern states. Unimportant. Brownish pustules on the lower leaf surface. 
Control: Same as for Fungus Leaf Spots (above) . 

12. Wetwood, Slime Flux — See under Elm. 

MULLEIN-PINK -See Carnation 

MUSCARI - See Tulip 

MUSKMELON - See Cucumber 

MUSTARD -See Cabbage 

MYOSOTIS-See Mertensia 

MYRICA-See Waxmyrtle 

MYRTLE (Myrtus); FEIJOA; GUAVA (Psidium) 

1. Powdery Mildew (myrtle) —Southern states. Grayish-white, powdery growth on 
the leaves. Most common in crowded, shaded areas. Control: Spray two or three 
times, 10 days apart, with Karathane. 

2. Leaf Spot — Small spots or blotches on the leaves. Control: Pick off and burn 
spotted leaves. 

i 3. Stem or Crown Rot (myrtle) — Plants wilt and die from rot at the soil line. Con- 
trol: Avoid overwatering, overcrowding, and planting in poorly drained soil. See 
under Delphinium. 

4. Root Rots — See under Apple, and (34) Root Rot under General Diseases. De- 
clining, sickly plants may be associated with root-feeding nematodes (e.g., burrow- 

, ing, dagger) . 

5. Anthracnose, Spot Anthracnose or Scab, Leaf and Fruit Spots, Fruit Rots (feijoa, 
guava) — Leaves and fruits are variously spotted and rotted. Ripe fruits may rot 
and be covered with a gray, brown, black, bluish-green, or pink mold. Control: 
Spray during rainy periods using captan or zineb. 

6. Root-knot — See (37) Root-knot under General Diseases. 



NASTURTIUM 293 

7. Wood Rots — Attacks guava. See (23) Wood Rot under General Diseases. 

8. Thread Blight (feijoa, guava) — Southeastern states. See under Walnut. 

MYRTLE BOXLEAF-See Bittersweet 
NANDINA, HEAVENLY BAMBOO (Nandina) 

1. Leaf Spot, Anthracnose — Southern states. Leaves are spotted. Centers of red spots 
may later turn almost black. Control: Pick off and burn spotted leaves. If serious 
enough, spray several times, 10 days apart, using zineb, maneb, or fixed copper. 

2. Root-knot — Plants may be sickly and stunted with nodule-like galls on the roots. 
See (37) Root-knot under General Diseases. 

3. Root Rot — See (34) Root Rot under General Diseases. May be associated with 
nematodes (e.g., dagger, lance, root-knot, spiral) . 

4. Chlorosis — Foliage turns yellow in alkaline soils. Plants may be stunted. See under 
Maple. 

NANNYBERRY - See Viburnum 

NARCISSUS - See Daffodil 

NASTURTIUM (Watercress) - See Cabbage 

NASTURTIUM, GARDEN; CANARYBIRDFLOWER (Tropaeolum) 

1. Bacterial Wilt — Mostly southern states. Plants may turn yellow, wilt, and die be- 
fore blossoming. Stems near the soil line often appear water-soaked. Black streaks 
appear when the stem is cut through. Roots decay and turn black. Control: Re- 
move and burn infected plants. Plant in clean soil which has not grown wilted 
potato, tomato, eggplant, tobacco, or other plants. Rotate plantings. 

2. Fungus Leaf Spots — Spots of various sizes, shapes, and colors on the leaves. Leaves 
may wither and drop early. Heterosporium spot may also cause rotting of the 
stems. It is severe in California along the coast. Control: If serious enough, apply 
zineb, maneb, or fixed copper at about weekly intervals during rainy weather. Com- 
mercial seedsmen control Heterosporium, which is seed-borne, by soaking the seed 
in hot water (page 429) . Presoak seed 1 hour in cool tap water. 

3. Bacterial Leaf Spot — Small, water-soaked, brownish spots on the leaves. Leaves may 
later rot. Control: Pick off and burn spotted leaves. Spraying as for Fungus Leaf 
Spots (above) may be beneficial. 

4. Mosaics — Symptoms highly variable. Yellow spotting and mottling of the leaves. 
Young leaves may be ruffled and cupped. Large, yellow to brown, arrow-shaped 
blotches or white, dead ringspots may also be found on the leaves. Flowers show 
a distinctive color break. May be small and crinkled. Control: Destroy infected 
plants when first found. Keep down weeds. Spray or dust weekly with a mixture 
of malathion and DDT to control aphids which transmit the viruses. 

5. Spotted Wilt — Numerous, yellowish to brown or dead spots and blotches develop 
on the leaves. Leaves are distorted, cupped, stunted, and may show a yellowish 
mottling. Plants are usually stunted. Control: Same as for Mosaics (above) . The 
virus is spread by thrips. 

6. Ringspot — Leaves mottled light and dark green with yellowish-green and yellow 
ring and line patterns or yellowish spots bordering the veins. Leaves may be 
crinkled, stunted, and partly dead. Plants may apparently recover and appear 
normal. Control: Same as for Mosaics (above) . 



294 NATAL-PLUM 

7. Curly-top — Older leaves are usually yellow. Numerous shoots are produced with 
dwarfed, cupped leaves. Flower parts of immature flowers are withered and dry. 
Flower buds are usually dwarfed and yellow. May fail to open. Control: Same as 
for Mosaics (above) . 

8. Aster Yellows — Plants stunted, yellow, and bushy. Control: Same as for Mosaics 

(above) . The virus is spread by leafhoppers. 

9. Root-knot, Root Gall — Small knots or galls on the roots. Plants may appear 
stunted and sickly. Control: See (37) Root-knot under General Diseases. 

10. Fasciation — See (28) Leafy Gall under General Diseases. 

11. Rust — Utah. Small, yellowish pustules on the leaves. Alternate hosts are wild 
grasses (Aristida and Distichlis). Control: Same as for Fungus Leaf Spots (above) . 

NATAL-PLUM - See Oleander 

NECTARINE - See Peach 

NELUMBO-See Waterlily 

NEMOPANTHUS - See Holly 

NEMOPHILA - See Phacelia 

NEPETA-See Salvia 

NEPHROLEPIS-See Ferns 

NEPHTHYTIS-See Calla 

NERINE-See Daffodil 

NERIUM-See Oleander 

NEW GUINEA BEAN - See Cucumber 

NEW JERSEY-TEA, JERSEY-TEA, DELISLE CEANOTHUS (Ceanoffius; 

1. Leaf Spots — Common. Small, more or less round spots on the leaves. Control: Not 
usually necessary. If serious enough, spray during rainy periods using zineb or 
maneb. 

2. Powdery Mildew — Widespread in late summer and fall. Powdery, white mold 
patches on the leaves. Control: Apply sulfur or Kara thane weekly, starting when 
mildew first appears. 

3. Rust — Small, yellowish spots on the leaves. Alternate hosts are wild grasses. Con- 
trol: Same as for Leaf Spots (above) . 

4. Crown Gall — See under Apple, and (30) Crown Gall under General Diseases. 

5. Wood Rot — See under Birch, and (23) Wood Rot under General Diseases. 

6. Root Rot — See under Apple, and (34) Root Rot under General Diseases. 

7. Dieback, Canker — See under Apple and Maple. 

NEW ZEALAND SPINACH - See Beet 

NICANDRA, NICOTIANA, NIEREMBERGIA, NIGHTSHADE - See Tomato 

NINEBARK [COMMON, ILLINOIS] (Physocarpus) 

1. Leaf Spots — Not serious. See under Maple. 

2. Powdery Mildew — Not serious. See under Birch. 

3. Wood Rot — See under Birch. 

4. Root Rot — See (34) Root Rot under General Diseases. 

5. Fire Blight — See under Apple. 



OAK 295 

NORFOLK ISLAND PINE -See Araucaria 

NOTHOSCORDUM - See Onion 

NUPHAR, NYMPHAEA-See Waterlily 

NYSSA — See Dogwood 

OAK [ BLACK, BLACKJACK, BUR, CHESTNUT (CHINESE, SWAMP or 

BASKET, CHINQUAPIN and DWARF CHINQUAPIN), COLUMNAR ENGLISH, 

CORK, ENGLISH, HOLM or HOLLY, LAUREL, LIVE (CALIFORNIA, CANYON, 

INTERIOR, SOUTHERN), PIN and NORTHERN PIN, POST, OVERCUP, RED, 

SCARLET, SHINGLE, SHUMARD, TEXAS, TURKEY, WATER, 

WHITE (OREGON, ROCKY MOUNTAIN, SWAMP, VALLEY), and WILLOW ] 

(Quercus); TANBARK-OAK (Lithocarpus) 

1. Oak Wilt — Serious over much of the eastern half of the United States. All oaks 
are susceptible. Chinese and American chestnuts, tanbark-oak, and chinquapin may 
also be infected. Uncommon on planted specimen trees. Leaves may turn a pale 
or dull green or be water-soaked, curl, progressively become more yellowed or 
bronzed from the tips and margins inward. Leaves on the upper branches are 
usually affected and drop first. Red and black oaks die in a few weeks. Individual 
white or bur oaks die back slowly (becoming stag-headed) over a period of several 
years or longer. Dark streaks can often be seen in the wood just under the bark of 
wilting branches. See Figure 142. The causal fungus may spread to nearby trees 
by underground root grafts or insects. Control: Remove and burn all infected and 
dead oaks as soon as possible. If other oaks are nearby on the property, dig a 
trench 4 feet deep, or poison all oaks with brush-killer (50:50 mixture of 2,4-D and 
2,4,5-T in fuel oil) or Ammate in a 50-foot circle from an infected tree. Do not 
injure or prune trees from April through June. If wounds are made, paint them 
promptly with a tree wound dressing (page 25) . Check with your nurseryman, 
county agent, or extension plant pathologist. Infected trees cannot be cured. 

2. Anthracnose, Leaf and Twig Blight — White oak is very susceptible. Most serious 
on the bottom half of trees in shaded areas during moist spring weather. Leaves 
turn brown and curl from the margins giving a scorched appearance. Small to 
large, irregular, light brown spots occur on black and red oak leaves. The spots 
often enlarge along the veins. Weakened trees may die if leaves drop early. See 
Figure 143. Control: Same as for Sycamore Anthracnose. Apply phenyl mercury 
as the buds are swelling in early spring. 

3. Leaf Blister, Leaf Curl (oaks) — General in cool, wet springs. Yellowish-green to 
gray, reddish, purple, yellow or brown, more or less round, raised blisters on the 
upper leaf surface (Figure 144) . Trees may appear scorched. Affected leaves may 
pucker or curl and drop in large numbers, weakening affected trees. Control: If 
practical, spray 1 to 2 weeks before the buds swell, using zineb, maneb, ferbam, 
dichlone, captan, or fixed copper. Collect and burn fallen leaves. 

4. Leaf Spots, Spot Anthracnose — Numerous spots of various sizes, shapes, and colors 
develop on the leaves in wet seasons. If severe, some leaves may wither and drop 
early. Control: Same as for Anthracnose (above) . 

5. Wood Rots, Heart Rots, Butt Rot — Cosmopolitan. See under Birch, and (23) 
Wood Rot under General Diseases. 

6. Twig Blights, Dieback — Cosmopolitan. Leaves scattered over the tree suddenly 
blight, curl, and hang downward. Twigs and small branches die back from sunken, 
girdling cankers. Control: See under Maple. 




Fig. 142. Oak wilt. A. Gross symptoms of red or black oaks (insert shows grafting of 
roots), B. Red oak leaf and twig symptoms. 




Fig. 142C. "Stag-head" of 
white oak. (Iowa State Uni- 
versity photo) 



OAK 



297 




Fig. 143. Oak anthracnose. 



Fig. 144. Oak leaf blister or leaf curl. 
(Courtesy Dr. V. H. Young) 



7. Branch and Trunk Cankers — Widespread. Discolored, enlarging, flattened or sunk- 
en cankers on the branches or trunk. Small trees may be killed. See under Elm. 

8. Root Rots — Cosmopolitan. Trees lack vigor, decline. Foliage is thin and sickly. 
Leaves may turn yellow, wither, and drop early. Stag-headed, dead branches are 
common. Trunk may break over during high winds. Roots and the base of the 
trunk are partially or completely rotted. Coarse strands of white mold growing just 
under the bark are common. Clumps of toadstools may appear near the trunk 
base. Control: See under Apple, and (34) Root Rot under General Diseases. 

9. Crown Gall — See under Apple, and (30) Crown Gall under General Diseases. 

10. Leaf Rusts — Minor problem. Small yellowish spots on the underleaf surface. Later, 
brown pustules develop. Alternate hosts include 2- and 3-needle pines. Control: 
None needed. 

11. Chlorosis, Iron Deficiency — See under Maple. Pin and willow oaks are very sus- 
ceptible in neutral and alkaline soils. Twig growth is stunted. May die back. 

12. Powdery Mildews (oak) —General. May cause injury in southern and western 
states. White to brown, powdery mold on undersides of leaves, new shoots, and 
buds. Leaves may be stunted, yellowish, wither, and drop early. Twigs may be 
stunted. Produce witches'-brooms of live oak in California. Oaks vary greatly in 
susceptibility. Control: If practical, spray when mildew is first evident. Use sulfur 
or Karathane. Prune out witches'-brooms on live oak along the Pacific Coast. Apply 
a dormant spray of lime-sulfur (1 to 50 dilution) . 

IS. Leaf Scorch — Browning or scorching of leaves between the veins or along the 
margins following hot, dry, windy weather in July and August. Control: Water 
during summer dry periods. Prune and fertilize to increase vigor. 

14. Sooty Mold, Black Mildew — Primarily southern states. Purplish-black mold patches 



298 OCEANSPRAY 

on the foliage. Often follows insect attacks. Control: See (12) Sooty Mold under 
General Diseases. 

15. Verticillium Wilt (oak) —See under Maple. 

16. Wetwood, Slime Flux — See under Elm. 

17. Mistletoe — See (39) Mistletoe under General Diseases. 

18. Bark Patch of White Oak — Small to large, irregular, smooth, light-gray, sunken 
patches on the dead bark. Trees are not injured. 

19. Bleeding Can ker — Northeastern states. See under Beech and Maple. 

20. Felt Fungus — Southern states on neglected willow and water oaks. Smooth, shiny, 
chocolate-brown to almost black growth on the bark. See under Hackberry. 

21. Root-feeding Nematodes (dagger, lance, needle, pin, ring, root-knot, root-lesion, 
sheath, spear, spiral, stem, sting, stubby-root, stylet or stunt, trophotylenchulus) — 
May be associated with Root Rots (above) and sickly, declining trees. Control: See 
under Peach. 

OCEANSPRAY -See Holodiscus 

OCIMUM-See Salvia 

OCONEE-BELLS - See Galax 

ODONTOGLOSSUM - See Orchids 

OENOTHERA —See Evening-primrose 

OKRA-See Hollyhock 

OLEA — See Osmanthus 

OLEANDER (Nerium); CARISSA, HEDGETHORN, CARANDA or PERUNKILA, 

NATAL-PLUM (Carissa); FRANGIPANI (Plumeria); CRAPE-JASMINE 

(Tabernaemontana); CONFEDERATE-JASMINE (Trachelospermum) 

1. Leaf Spots, Spot Anlhracnose or Scab — Small to large spots of various colors and 
shapes on leaves and seedpods. Infected leaves may wither and fall early. Control: 
Pick off and burn spotted leaves. Spraying at 10-day intervals during rainy periods 
should prove beneficial. Use zineb or maneb. 

2. Bacterial Gall or Knot (oleander) — Wartlike galls are formed on the branches, 
shoots, leaves, and even on flowers. Young leaves and seedpods may be distorted 
and curled. Canker-like tumors are formed on the older branches which are soft 
or spongy and rough. Such galls darken with age. Control: Prune out and burn 
infected parts. Be sure to dip shears in alcohol between cuts. Propagate only from 
healthy plants. Control scales, aphids, and mealybugs by spraying regularly with 
malathion or lindane. 

3. Sooty Mold, Black Mildew — Gulf states. Black, powdery patches on the foliage 
following insect attacks. Control: Control insects with malathion or lindane sprays. 

4. Cankers, Dieback — Shoots and twigs die back from discolored cankers. Control: 
Prune out and burn infected parts. Make cuts several inches below any sign of 
infection. Spraying as for Leaf Spots (above) should be beneficial. 

5. Root-knot — See under Peach, and (37) Root-knot under General Diseases. 

6. Root Rots — See under Apple, and (34) Root Rot under General Diseases. May be 
associated with nematodes (e.g., burrowing, dagger, root-knot, stubby-root) . 

7. Rust (frangipani) — Reddish-brown, later black, powdery pustules on the leaves. 
Control: Same as for Leaf Spots (above) . 

8. Mistletoe (frangipani) — See (39) Mistletoe under General Diseases. 



ONION 299 



OLIVE — See Osmanthus 
ONCIDIUM-See Orchids 

ONION [COMMON, WELSH or SPANISH, WILD], CHIVES, GARLIC, LEEK, 

LILY LEEK, ORNAMENTAL ALLIUM, SHALLOT (Allium); 

FALSE-GARLIC (Nothoscordum) 

l.Neck Rot, Gray-mold Blight, Leaf Blight — Widespread. Leaves may die in the 
field. Soft, sunken, spongy areas on the neck, in the field or more commonly in 
storage, which spread down into the bulb. A gray mold may grow over and between 
the bulb scales. Neck and bulb soften and appear somewhat brownish and cooked. 
Bulbs later mummify and may develop small to large, black, crustlike masses 
(sclerotia) . This is a serious storage problem. White onions are usually much more 
susceptible than colored types. Bacterial Soft Rot commonly follows. See Figure 49B, 
and (36) Bulb Rots under General Diseases. Control: Sort bulbs well before stor- 
age. Avoid wounding. Cure mature bulbs at 90° to 120° F. for 2 to 3 days (or 
60° to 80° F. for 2 weeks) . Then store only healthy, mature, well-dried onions at 
32° to 36° F. with good ventilation in slatted crates. Keep the humidity as low as 
practical. Collect and burn plant debris after harvest. Spray in the field as for 
Blast, Downy Mildew, and Purple Blotch (all below) during wet periods. Avoid 
late fertilizer applications, especially those containing nitrogen. Keep down weeds. 
Plant in well-drained soil. 

2. Bacterial Soft Rot — Widespread and destructive. Bulb is water-soaked then mushy, 
slimy, and usually foul-smelling. Follows injury (sunscald, frost, insects, cultivator 
wounds, other diseases) . Control: Same as for Neck Rot (above) . 

3. Bulb Rots — General in moist soils. Leaves often turn yellow or wilt and die back. 
May collapse. Roots and bulb decay. Bulb may be covered with a white, black, 
lemon-yellow, bluish-green, or gray mold growth. Bacterial Soft Rot may follow. 
Loss occurs in both field and storage. See Figure 49B under General Diseases. 
Control: Plant disease-free sets and transplants in clean, well-drained soil. Dip 
shallot bulbs in Dowcide B (1 ounce in 3 gallons) for 15 minutes just before plant- 
ing. Long rotation. Keep down weeds. Collect and burn crop debris after harvest. 
Cure and sort bulbs well before storage as for Neck Rot (above) . Keep plants 
growing vigorously throughout the season. Control other diseases. Onion varieties 
differ in resistance. Control onion maggots using seed pelleted with aldrin, dieldrin, 
or Diazinon or apply a 4-inch band of one of these chemicals in the planter furrow. 
Check with your county agent or extension entomologist and follow the manu- 
facturer's directions. Apply Terraclor (PCNB) to garlic or shallot sets or apply as 
a dust in the planting furrow. May combine with an insecticide (e.g., aldrin or 
dieldrin) . Avoid injuring bulbs. 

4. Smut — General, especially in northern states. Elongated, blister-like streaks occur 
within bulb scales or seedling leaves. Streaks are filled with dark brown to black, 
powdery masses which later break out. Leaves are curled, swollen, and distorted. 
Plants are stunted. Most infected seedlings die early. See Figure 25B under General 
Diseases. Control: Set out disease-free sets or transplants or grow seedlings in clean 
soil. Treat seed in the planter using 1 ounce of thiram or captan for each ounce of 
seed. Hexachlorobenzene (or HCB) sold as Anticarie 80 has also given excellent 
control. Follow the manufacturer's recommendations. Commercial growers often 
drip formaldehyde solution into the planting furrow (1 part formalin to 100 parts 
of water) using 1 pint to 35 feet of row when the soil surface is rather dry. Nabam 
and urea-formaldehyde (UF-85, N-dure, Uracide) are also effective liquid treat- 
ments at a 1 per cent concentration and applied like formaldehyde. Smut-resistant 
onions, where adapted: Beltsville Bunching, Evergreen Bunch, Nebuka Bunching, 
White Welsh, and Winterbeck. Chives is resistant while garlic is apparently im- 
mune. 



300 ONION 

5. Blast or Tip Blight, Tipburn — Widespread in northern states. Small, pale, paper- 
like flecks or spots on the leaves during or following overcast, humid weather. Leaf 
tips die back. Leaves may turn light tan, then brown, collapse, and die. Bulbs are 
undersized and immature. Control: Plant disease-free sets or transplants in well- 
drained soil where air circulation is good. Keep down weeds. Four-year rotation. 
Destroy plant debris after harvest. Avoid overcrowding and overfertilizing with 
nitrogen. Spray with zineb, maneb, ferbam, or captan, plus spreader-sticker, at 
weekly intervals, starting when seedlings are 3 to 4 inches tall. Six to 10 applica- 
tions may be needed. Control thrips (using DDT and malathion) and other 
diseases. 

6. Downy Mildew — General. During cool, humid weather, sunken, dull pale green 
to grayish areas develop in the leaves which become covered with a pale purplish, 
fuzzy mold. Leaves may turn yellow, die back, and break over. Other plants may 
be stunted with distorted, pale green leaves. Bulbs are undersized and often soft 
and immature. Resistant onions (e.g., Calred) appear promising. Control: Same as 
for Blast (above) . Red onions have some resistance. 

7. Purple Blotch, Alternaria Leaf Blights — Widespread in wet seasons. Small to large, 
gray to purplish, sunken blotches on the leaves, flower stalk, and bulb. A black 
mold may grow on affected areas in moist weather. Leaves turn yellow, die back, 
and collapse. Bulbs often rot starting at the neck. Bulb tissue is a deep yellow, 
then gradually turns wine-colored. May be serious in storage. Common following 
insect injury or other diseases. Sweet Spanish onion is very susceptible. Control: 
Same as for Neck Rot (above) . Treat seed as for Smut (above) . Four-year rotation. 
Plant in well-drained soil. Apply maneb, zineb, or Dyrene at weekly intervals. Add 
detergent or spreader-sticker to insure wetting of the foliage. Control thrips with 
DDT, malathion, or dieldrin. Onion varieties differ in resistance. Those with 
waxy foliage are resistant. 

8. Pink Root, Fusarium Root Rot — Widespread. Pink Root is most common on 
onions, garlic, and shallots. Seedlings wilt and die. Leaves often die back from the 
tips. Plants are stunted. Roots turn pink or yellowish-brown, shrivel, darken, and 
die. Bulbs may be undersized. Often follows cold, heat, drought, flooding, lack of 
fertilizer, or other unfavorable growing conditions. Control: Plant sets or transplants 
grown in disease-free soil. Plant in clean, well-drained, fertile soil or fumigate 
(pages 440-44) infested soil before planting. Keep plants growing vigorously. Five- 
or 6-year rotation. Onion hybrids and varieties resistant to Pink Root, where 
adapted: Beltsville Bunching, Colorado No. 6, Early Crystal 281, Eclipse L365, 
Evergreen Bunch, Excel L35, Granex, L303, and Nebuka Bunching. Much more re- 
sistant hybrids should be available soon. Check with your state or extension plant 
pathologist. Leek and chives are highly resistant to Pink Root. Resistant shallots: 
Louisiana Pearl, Evergreen. 

9. Bloat, Stem and Bulb Nematode (primarily garlic, onion, and shallot) — Seedlings 
stunted, pale, twisted, and deformed. Infested sets develop much stunted, yellow, 
and wilted foliage. Outer bulb scales are soft and mealy in texture. Inner bulb 
scales are swollen. Splitting or double bulbs are common. Plants die gradually. 
Root- and bulb-rotting fungi and bacteria often follow. Bulbs are lightweight, 
punky, store poorly. Worse in wet seasons and on heavy soils. See Figure 51 A under 
General Diseases. Control: Plant disease-free sets, transplants, or cloves in clean 
soil. Or plant in soil fumigated in the fall before planting. Use D-D or Telone. 
Disinfect tools and equipment. Dig up and destroy infected plants when first 
found. Thoroughly clean up and burn all plant debris after harvest. Rotation 3 or 
4 years. Don't save bulbs grown in infested soil! Soak suspicious shallot bulblets 

(cloves) in hot water (115° F.) for 1 hour. Soak garlic cloves in hot water (110° 



ONION 



301 



F.) and formalin (1:200 or 1 pint of 37-40 per cent formaldehyde in 25 gallons) 
for 3 hours just before planting. 

10. Root-knot — Tops sickly, pale green, and stunted. Small, thick-necked bulbs are 
produced. Small, round swellings form on the roots. Crooked roots are common. 
Control: If serious enough, apply D-D or Telone as for Bloat (above) . 

11. Smudge, Anthracnose (primarily white onions, false-garlic, leek, shallot) — General. 
Dark green to black, often ringed, unsightly blotches (made up of small dots) on 
bulb or neck. Usually at side or top. See Figure 145. Stored bulbs may shrivel 



Fig. 145. Onion smudge. 




slightly or sprout prematurely. Control: Plant colored onion varieties or disease- 
free sets. Otherwise, same as for Neck Rot (above) . Provide good ventilation in 
storage. Rotate. 
12. Yellow Dwarf, Mosaics, Yellows (false-garlic, garlic, onion, shallot, ornamental 
allium) — Widespread. Plants yellowed, or with yellow and green stripes. Usually 
severely stunted and crinkled. Flower stalks are dwarfed, curled, and twisted. Bulbs 
are undersized. Shallot leaves are spindly and yellowed. Seed sets and edible parts 
may not form. Certain onion varieties may show no symptoms. Control: Plant virus- 
free sets or transplants. Destroy volunteer or wild onions. Isolate bulb- from seed- 
producing fields as far as possible. Keep down weeds. Control aphids which transmit 
the virus. Use malathion. Tolerant onion varieties: Beltsville Bunching, Burrell's 
Sweet Spanish, Colorado No. 6, Crystal Grano, Early Grano, Early Yellow Babosa, 
Lord Howe Island, Nebuka Bunching, Riverside Sweet Spanish, San Joaquin, 
Spanish Crystal Grano, Utah Sweet Spanish, White Babosa, White Sweet Spanish, 
and Yellow Sweet Spanish. Resistant shallots are also available. 



302 ONOCLEA 

13. Aster Yellows (garlic, onion, shallot) —Plants gradually turn a bright yellow, 
often starting first on one side of the plant. All leaves may turn yellow at about 
the same time. If severe, bulbs may not form. Control: Destroy infected plants 
when first found. Plow under crop debris cleanly after harvest. Use virus-free sets. 

14. Rusts — Occasional. Attack garlic, false-garlic, onion, shallot, chives, and orna- 
mental allium. Small, light yellow to orange or reddish, then lead-colored to black, 
powdery pustules on the leaves and stalk. If severe, leaves may turn yellow, wither, 
and die early. Control: Rotate. Collect and burn plant debris after harvest. Keep 
down weeds. Spraying as for Blast or Downy Mildew (both above) should keep 
Rusts in check. Use ferbam, zineb, or maneb. 

15. Sunscald — Bleached, then soft, slippery areas, especially on immature bulbs of 
white varieties of onions. Bacterial Soft Rot often follows. Control: Protect bulbs 
from hot sun during curing and harvesting by covering with tops. Harvest later 
in the day. 

16. Minor Leaf Spots and Blights, Tip Dieback — White, gray, pale green, yellow to 
pale brown or black spots and blotches on the leaves which may be covered with 
dark mold growth in damp weather. Leaves often die back from the tip or break 
over. Control: Same as for Blast, Downy Mildew, and Purple Blotch (all above) . 

17. Freezing Injury — Tissues in cut bulbs are water-soaked and more or less transparent 
with scattered opaque areas. Bacterial Soft Rot commonly follows. Control: Avoid 
storage temperatures below 32° F. Bermuda and Sweet Spanish onions are much 
more susceptible than the Globe varieties. 

18. Damping-off — Seedlings wilt and collapse from rot at the soil line. Often occurs 
in more or less circular patches. Control: Follow the best cultural practices. Treat 
seed and soil as for Smut (above) . Spray young seedlings at 5- to 7-day intervals 
using zineb (\\/ 2 tablespoons per gallon). 

19. Verticillium Wilt — See (15B) Verticillium Wilt under General Diseases. 

20. Scab (onion) —See (14) Scab under General Diseases. 

21. Bacterial Leaf Streak (onion) —Colorado. Mottled brown streaks form on older 
leaves and leaf sheaths in warm weather. Control: Same as for Neck Rot (above) . 

22. Other Root-feeding Nematodes (lance, pin, root-lesion, spiral, sting, stylet or stunt, 
stubby-root) — Associated with stunted, sickly plants. Roots stubby, short, and dis- 
colored. May provide wounds for root- and bulb-rotting organisms to enter. Con- 
trol: Same as for Root-knot (above) . 

ONOCLEA -See Ferns 

ONOSMODIUM - See Mertensia 

OPHIOGLOSSUM - See Ferns 

OPUNTIA-See Cactus 

ORANGE — See Citrus 

ORANGE SUNFLOWER - See Chrysanthemum 

ORCHIDS: ANGRAECUM, CATASETUM, CATTLEYA, CYMBIDIUM, 

CYPRIPEDIUM, DENDROBIUM, EPIDENDRUM, GRAMMATOPHYLLUM, 

LAELIA, LYCASTE, MILTONIA, ODONTOGLOSSUM, ONCIDIUM, 

PHALAENOPSIS, SPATHOGLOTTIS, STANHOPEA, VANDA, and 

ZYGOPETALUM 

I. Seed Rot, Mold, Seedling Blight — Common in culture flasks. Seeds rot. Seedlings 
are weak and collapse. May be covered with mold growth, often blue-green in color. 



ORCHIDS 303 



Control: Sterilize seeds by soaking several hours in small bottles (i/ 2 inch by 2 
inches) filled i/ 2 inch deep with distilled water. Then add i/ 2 ounce of distilled 
water in which a chlorine tablet is dissolved. Shake for 3 to 4 minutes and pour 
into sterile flasks containing agar to let the seed germinate. Rotate culture flasks 
evenly to distribute the seed. Then pour off the solution. 

2. Leaf Blight, Pythium Black Rot, Damping-off — Common in community pots. 
Round to oval, translucent or water-soaked, dark brown or blackish spots, some- 
times with zoned, light brown borders, develop on the leaves. Spots enlarge rapidly 
in moist weather until the whole leaf may soften, wither, and collapse. Seedlings 
often wilt and topple over. Pseudobulbs, rhizomes, roots, and flower buds may 
also rot. Control: Destroy infected seedlings. Cut out and burn infected parts on 
older plants. Carefully remove rotting leaves and pseudobulbs. When dividing 
plants, sterilize knives by dipping in 70 per cent denatured alcohol. Keep the 
foliage as dry as possible. Avoid excess moisture. Keep the humidity down. Space 
plants for good air circulation. Isolate diseased plants. Drench seedlings or dip 
infected plants, pot and all, for an hour (large plants for 2 or 3 hours) in Bioquin 
1 or Natriphene 1:2,000 (1 teaspoonful in 2i/£ gallons of water) following the 
manufacturer's directions. If rot continues, repeat the treatment a week later. 

3. Leaf Spots, Leaf Blotch, Anthracnose, Black Spot — Round to irregular spots on 
the leaves. Often sunken and sharply defined. Spots may later be ringed. Disease 
may start at the leaf tips and progress downwards. If severe, leaves may darken and 
die. Control: Spray with Bioquin 1 (1:1,000), fixed copper, or zineb. Keep the 
humidity down and the foliage as dry as possible. Avoid overfertilizing with nitro- 
gen. Increase both light and air circulation. Do not propagate from infected plants. 

A. Stem, Collar, and Root Rots — Serious on many orchids. Leaves wilt, wither, and 
usually collapse from a rotting of the stem base or root collar. Roots may decay. A 
white or brown mold may grow on the rotting tissues. See also Root Nematodes 
(below) . Control: Plant disease-free seedlings in a sterile medium. See Seed Rot 
(above) . Destroy infected plants. Avoid overwatering or wounding plants, exces- 
sive humidity, and temperature. Soak plant, pot and all, for an hour in a solution of 
Bioquin 1 or Natriphene (1 teaspoon in 2\/ 2 gallons of water) following the 
manufacturer's directions. 

5. Petal Blights, Brown Speck, Gray-mold Blight — Small tan spots on the flowers. 
May be bordered with delicate pink rings. Spots enlarge in cool, damp weather, 
forming brown blotches. Petals may be destroyed. A grayish-brown mold may de- 
velop on the decaying tissue. Control: Carefully cut and burn infected flowers as 
soon as found. Same cultural practices as for Leaf Spots (above) . 

6. Bacterial Soft Rot, Brown Spot or Rot — Small, soft, water-soaked, dark green, 
amber-colored, brown or black spots on the leaves. Leaves may soon collapse, turn 
yellow or brown, mushy, and foul-smelling. Rotting crowns shrivel. Leaves may 
drop early. Pseudobulbs and rhizomes may develop a soft, black, foul-smelling rot. 
Control: Avoid wounding plants. Remove rotted plant parts promptly. Separate 
diseased from healthy plants. Disinfect knife between cuts by dipping in household 
bleach or mercury (e.g., Semesan or a 1:1,000 solution of mercuric chloride. See 
page 427 for precautions) . Keep plant foliage as dry as possible. Separate diseased 
from healthy plants. Dipping plants as for Leaf Blight (above) is beneficial. Or 
swab small infected areas on leaves with a 1:1,000 solution of mercuric chloride. 
Repeat as necessary. 

7. Rusts — Yellowish-green spots on the upper leaf surface with bright, yellowish- 
orange, powdery pustules on the corresponding underside. Blooms may not develop. 
Plants are stunted. Control: Destroy rusted leaves. Otherwise same as for Leaf 
Spots (above) . 



304 ORCHIDS 

8. Fusarium Wilt (cattleya) — Leaves wilt, wither, and drop off. Pseudobulbs, roots, 
and rhizomes die. Flowers are stunted and fewer in number. Control: Plant in a 
sterile rooting medium. Destroy infected plants. 

9. Mosaics, Mottle, Leaf Necrosis (many genera) — General. Symptoms variable de- 
pending on the viruses involved, the orchids, and environmental conditions. In 
Cattleyas and related orchids infection is expressed as yellowish or sunken, red- 
dish-brown to black patterns, ringspots, irregular spots, mottling, or streaks in the 
leaves. Leaves may die early. Fewer and smaller flowers are produced. New leaf 
growth is stunted, cupped, and often pock-marked. In Cymbidiums symptoms are 
variable in pattern and severity. The spots are often first elongated and yellowish. 
Later these areas enlarge and become more defined. Leaves are mildly or severely 
mottled. Dark streaks, spots, rings, and patterns may develop in the older leaves. 
Severely infected leaves may drop early. Growth may be stunted. In Sfratho glottis 
diamond-shaped, dead spots are formed. New growth is mildly to severely mottled. 
Later, concentric ring patterns are formed. Small, solid, elliptical, reddish to red- 
dish-brown spots are formed in Miltonia leaves. In Oncidium conspicuous, irregu- 
lar, yellowish spots and streaks or a light green mosaic mottle develops in the leaves. 
Dark brown to black spots or sunken streaks form on the underside of Epidendrum 
leaves. Halo-like, brownish rings with dark centers form in very young leaves. In 
Odontoglossum an irregular, light green to yellowish mosaic pattern is formed. Or 
streaks and small rings develop in the leaves which become rusty-colored or dead in 
some cases. Leaves may be stunted. Narrow, longitudinal, light to dark green streaks 
form in Lycaste leaves. Control: Destroy infected plants. When dividing or harvest- 
ing flowers, disinfect pruning tools between cuts by dipping in 70 per cent de- 
natured alcohol. Keep healthy and virus-infected plants separated. Select virus-free 
propagation stock and seedlings. Malathion sprays control aphids which transmit 
the viruses. Keep down weeds in and around growing orchids. Check with the plant 
pathology department at your land-grant institution concerning: antivirus antisera 
and special ring tests for determining infected plants. Use seedlings since viruses 
do not invade the seed of orchids. 

10. Flower Breaking (cattleya, cymbidium, dendrobium, oncidium, spathoglottis, vanda, 
etc.) — Leaves may show an irregular, mild to severe mosaic mottling and some 
malformation. Flower petals may be mottled, somewhat distorted, or show irregular 
and abnormal color streaks and blotches. Flower sepals and petals may be rolled 
and twisted. Virus is symptomless in some plants. The center shoot of Spathoglottis 
may become blackened. Control: Same as for Mosaics (above) . 

11. Ringspots (cymbidium, dendrobium, laelia, miltonia, odontoglossum, stanhopea, 
vanda) — Symptoms variable. Small, dead (or light green to pale yellow) spots, 
lines, or rings — partial or complete — develop on the upper leaf surface. The single 
or concentric rings may later be totally dead enclosing a central light green or 
yellow "island." Rings may overlap or run together forming large compound 
patterns. Some leaves may turn yellow and drop early. If severe, the entire plant 
may die. Control: Same as for Mosaics (above) . 

12. Leaf Nematodes — Angular, brown or blackish spots wedged between the larger 
veins. Infested leaves later die. The stem and bulb nematode may cause some 
malformation of the lower leaves which become brittle and break off easily. Flower 
buds may turn yellow, then brown and shrivel without opening. Control: Propagate 
from healthy plants into a sterile rooting medium. Keep foliage as dry as possible. 
Cut off and burn infested leaves. Spray weekly with malathion plus spreader- 



OSMANTHUS 305 



sticker. Keep orchids away from ferns, phlox, and other susceptible plants. Dis 
infest Vanda cuttings by soaking in hot water (115° F.) for 10 minutes. 

13. Root Nematodes (e.g., root-lesion or meadow) —Usually found associated with 
root and bulb rots and yellowish leaves. Older leaves die prematurely. Control: 
Same as for Stem Rots (above) . 

14. Tipburn (cymbidium) —Tips of older leaves darken and die back. Various molds 
may grow on the dead tissue in moist weather. Control: Plant in light, well-drained, 
sterile soil low in soluble salts. Apply fertilizers frequently but in very dilute form. 
Use slowly available forms of nitrogen. Check with your florist, garden supply 
dealer, or extension horticulturist. 

For additional information on orchid problems read a book such as The Orchids: 
A Scientific Survey, published by the Ronald Press Co. 

OREGON-GRAPE - See Barberry 
ORNITHOGALUM - See Tulip 

OSAGE-ORANGE (Madura) 

1. Rust — Southern states. Minor disease. Reddish-brown, powdery pustules on the 
leaves. Control: Unnecessary. 

2. Leaf Spots, Leaf Blight — Unimportant. Small to large, tan, gray, or "cottony" 
spots on the leaves. Control: Collect and burn fallen leaves. 

3. Verticillium Wilt — See under Maple, and (15B) Verticillium Wilt under General 
Diseases. 

4. Mistletoe — See (39) Mistletoe under General Diseases. 

5. Damping-off — See under Pine. 

6. Root Rot — See (34) Root Rot under General Diseases. 

OSIER — See Dogwood and Willow 

OSMANTHUS [CHINESE, HOLLY], SWEETOLIVE, WILD OLIVE, 
DEVILWOOD (Osmanthus); OLIVE (Olea) 

1. Leaf Spots, Black Leaf Spot, Anthracnose — Small to large spots on the leaves, often 
black in color. Spots may also occur on olive fruit. Control: Collect and burn fallen 
leaves. Keep trees pruned. If serious enough, try spraying during rainy periods 
using zineb, maneb, or captan. 

2. Sooty Molds, Black Mildew — Gulf states. Black, moldy patches on the leaves. Often 
follows insect attacks. Control: Apply malathion sprays to keep insects in check. 

3. Root Rots — See under Apple, and (34) Root Rot under General Diseases. May be 
associated with nematodes (e.g., meadow or root-lesion, citrus) . 

4. Root-knot — See under Peach, and (37) Root-knot under General Diseases. 

5. Bacterial Knot (olive) — California. Irregular, spongy to hard, knotty galls, up to 
several inches in diameter, may appear on leaf and fruit stems, twigs, branches, 
trunk, and roots. Shoots may be stunted and die back. Entire trees may die. Con- 
trol: Cut out galls carefully, disinfecting tools between cuts by dipping in 70 per 
cent denatured alcohol or household bleach. Paint over larger wounds with 
bordeaux paste or treat galls as outlined under Peach, Crown Gall. Plant healthy 
nursery stock. Follow the spray program recommended for your area. 

6. Mistletoe (osmanthus) — See (39) Mistletoe under General Diseases. 

7. Verticillium Wilt (olive) — See (15B) Verticillium Wilt under General Diseases. 



306 OSMARONIA 

OSMARONIA - See Rose 

OSMORHIZA - See Celery 

OSMUNDA-See Ferns 

OSOBERRY-See Rose 

OSTRYA-See Birch 

OSWEGO-TEA-See Salvia 

OXALIS, WOODSORREL, LADYS-SORREL, SHAMROCK (Oxalis) 

1. Leaf Spots, Tar Spot — Spots of various shapes, colors, and sizes on the leaves. 
Control: Pick off and burn spotted leaves. If serious enough, spray at 10-day inter- 
vals using zineb, maneb, or fixed copper. 

2. Powdery Mildew — White, powdery blotches on the foliage. Control: Spray two to 
three times, 10 days apart, with Kara thane. 

3. Rusts — Yellow-orange, reddish-brown, or black, powdery pustules on the leaves. 
May be serious. Alternate hosts include wild grasses, corn, and Oregon-grape. 
Control: If serious enough, apply ferbam or zineb at 10-day intervals. 

4. Stem Nematode — See (20) Leaf Nematode under General Diseases. 

5. Root Rot — See under Geranium, and (34) Root Rot under General Diseases. 

6. Seed Smut — See (11) Smut under General Diseases. 

7. Curly-top — See under Beet, and (19) Curly-top under General Diseases. 

OXEYE, OXEYE DAISY - See Chrysanthemum 

OXLIP — See Primrose 

OXYBAPHUS - See Four-o'clock 

OXYDENDRUM - See Sorreltree 

PACHISTIMA-See Bittersweet 

PACHYCEREUS - See Cactus 

PACHYSANDRA, ALLEGANY; JAPANESE or MT. SPURGE (Pachysandra) 

1. Leaf Blight, Dieback, Stem Canker —Large, brown blotches on the leaves. Leaves 
are later brown to black and blighted. Stems are withered by dark cankers. Salmon- 
pink pustules cover affected parts in wet weather. Plants die out in patches. Com- 
mon after injury. Control: Control scales by malathion sprays. Mulch plants for 
the winter with a light material which does not hold moisture. Avoid excess mois- 
ture and overcrowding. Clean out and burn all infected plants. Spray the re- 
mainder thoroughly with bordeaux mixture. Repeat 7 to 10 days later. Or apply 
ferbam, or cap tan, plus spreader-sticker, three or four times, 7 to 10 days apart. 
Thin out thick beds to increase light and air circulation. 

2. Leaf Spots — Small spots on the leaves. Control: Rarely necessary. Spray as for Leaf 
Blight (above) . Thin out thick beds. 

3. Root-knot — Small galls form on the roots. See (37) Root-knot under General 
Diseases. 

4. Other Root-feeding Nematodes (dagger, lance, pin, root-lesion, spiral, stylet or 
stunt) —Associated with stunted, sickly plants. Control: Same as for Root-knot 
(above) . 



PALMS 307 



PAEONIA — See Delphinium 

PAGODATREE - See Honeylocust 

PAINTED-CUP — See Snapdragon 

PAINTED DAISY -See Chrysanthemum 

PAINTED-TONGUE - See Tomato 

PAK-CHOI-See Cabbage 

PALE LAUREL -See Blueberry 

PALAIS: QUEEN PALM or PLUMY-COCONUT (Arecastrum); 

SUGAR (Arenga); FISHTAIL (CaryofaJ; COCONUT (Cocos); 

CANARY DATE or DATE (Phoenix); CUBAN ROYAL and PUERTO RICO 

(Roysfonea;; PALMETTO, CABBAGE (Sabal); WASHINGTON (Washingtonia) 

1. False Smuts, Leaf Scab (date, palmetto, queen, royal, sugar, Washington) —Wide- 
spread. Numerous, small, yellow spots and small, black, hard warts or scabs on the 
leaves. Severely infected leaves soon die. Control: Cut out and burn infected leaves 
or parts of leaves. Indoors, keep water off the foliage. When disease is first evident, 
spray with a copper fungicide. Repeat sprays during cool, rainy weather. Thiram, 
zineb, or ziram may do just as well without causing injury. 

2. Leaf Spots or Blight, Anthracnose (coconut, date, fishtail, palmetto, queen, royal, 
Washington) — Widespread. Small to large, round to irregular spots of various 
colors on the leaves. Spots may run together forming large blotches. A brown blight 
may work downward from the leaf tip. Infections may cause rotting of the leaf bases. 
Leaves may die. See Figure 146. Control: Indoors, maintain sufficient light. Other- 
wise same as for False Smuts (above) . 

3. Stem (Trunk) and Root Rots, Wilt (coconut, date, royal, Washington) — Leaves 
may turn gray or yellow and wilt progressively up the plant. Later fall. Plants un- 
thrifty, often stunted, lack vigor. Gumming may be evident on the trunk. Small, 
black, club-shaped fruiting bodies may grow out from decaying roots. May be associ- 
ated with nematodes (e.g., burrowing, dagger, spiral) . Control: Plant potted palms 
in sterilized soil (pages 437-44) . Keep plants growing vigorously through fertilizing 
and watering. Avoid wounding roots or stem (trunk) . Coat wounds promptly with 
tree wound dressing (page 25) . 

4. Bud Rot, Wilts, Trunk Rot, Leaf Drop (coconut, palmetto, queen, Washington) — 
Soft, spongy, rot of stem (trunk) base. Leaves wilt and die in several months. 
Terminal bud develops a wet rot. Bud loosens and withers. Control: Cut out crown, 
infected buds, and leaves from diseased trees. Avoid trunk injuries. 

5. Black Scorch, Heart Bud Rot (coconut, date) — Dark brown to black hard spots 
in the leaves, leaf stalks, buds, and flowers. If severe, the heart leaves dry up. Con- 
trol: Cut out and bury or burn all infected plant parts. Disinfect pruning cuts. 
Copper sprays during rainy periods may be beneficial. 

6. Bacterial Wilt (coconut, Cuban royal) — Lower leaves turn gray and wilt. Later the 
trunk exudes gum. Finally the crown collapses. Control: Unknown. Plant disease- 
free plants in sterilized soil. Destroy infected plants when found. 

7. Penicillium Leaf Base Rot, Bud Rot, Trunk Canker, Gummosis (coconut, date, 
queen, Washington) — Serious along the southern Pacific Coast. Symptoms vari- 
able. Date palms: Linear streaks and a leaf base rot occur. Washington palms: 
Stunted, deformed leaves, dwarfed terminal growth, and bud rot. Queen or Coco- 
nut: Trunk canker. Leaf bases rot progressively upward on the tree. Trunk is weak- 
ened. Later breaks. Control: Treat trunk cankers early. Grow resistant Washington 



308 PALMS 




jHfefe 








UPPER SIDE 



Fig. 147. Violet scab or spot anthracnose. 



Fig. 146. Leaf spot of palm. 



palms (Washingtonia robusta). Check with the Department of Plant Pathology, 
University of California, Riverside, California. 

8. Root-knot and Other Nematodes (e.g., burrowing, lance, needle, root-lesion or 
meadow, spiral, stubby-root) — See under Peach, and (37) Root-knot under 
General Diseases. 

9. Black Mildews (palmetto) — Gulf states. Black, powdery patches on the leaves. 
Control: Spray with a fungicide plus malathion or lindane to control scales, mealy- 
bugs, aphids, and other insects. Follow the manufacturer's directions carefully. 

10. Sunscald — Indoor problem. Large, dry, leaf blotches with yellow centers and 
brown margins. Control: Provide more shade. 

11. Withered Leaf Tips — Indoor problem. Tips of leaves or even entire leaves may 
wither and die after being moved to a new location. Control: Avoid sudden changes 
in humidity (e.g., from a damp greenhouse to a dry living room) . Buy plants with 
tough, dark green leaves. Feed lightly with a balanced fertilizer. Avoid overwatering. 
Repot only when absolutely necessary. Keep plants out of air drafts. Raise the 
humidity in a dry room or spray leaves occasionally with water at room temper- 
ature. 

12. Chlorosis — Southeastern states. See under Walnut. 

13. Thread Blight — Southeastern states. See under Walnut. 

14. Fruit Rots (date) —Fruit rot. See (32) Fruit Rot under General Diseases. Control: 
Check with your state or extension plant pathologist. 

15. Felt Fungus — Southeastern states. See under Hackberrv. 



PANSY 309 



PANDANUS — See Screwpine 

PANSY [HORNED, TUFTED or BEDDING PANSY, VIOLET], VIOLET 
[CONFEDERATE, SWEET or FLORISTS', WILD] (Viola) 

1. Anthracnose, Leaf Spots, Spot Anthracnose or Scab — General. Small to large leaf 
spots of various sizes, shapes, and colors. Often with a distinct, dark margin. Spots 
may enlarge and run together forming irregular blotches. Similar spots may occur 
on the stems, petioles, flower petals, and seed capsules. Infected petals are distorted. 
Flowers may fail to produce seed. Entire plant may die. See Figure 147. Control: 
Collect and burn infected plant parts. Space plants. Rotate plantings. Destroy old 
tops in the fall. Indoors, keep water off the foliage and avoid dampness. Plant 
disease-free plants in a warm, dry location. Spray at 5- to 7-day intervals during wet 
weather using zineb, captan, ferbam, maneb, or fixed copper. Control insects with 
malathion. Plant disease-free seed. If in doubt, treat seed as for Wilt (below) . 

2. Gray-mold Blight, Botrytis B Ugh t — Common in wet springs. Soft, grayish-brown, 
rotted spots in the leaves, stems, and flower clusters. Spots enlarge rapidly in damp 
weather. Affected parts may be covered with a gray mold and become slimy. Control: 
Same as for Anthracnose (above) . 

3. Powdery Mildew — Whitish patches of mildew on the leaves. If severe, leaves may 
turn brown and wither. Control: If serious enough, apply sulfur or Karathane two 
or three times, 10 to 14 days apart. Do not use when the temperature is 85° F. or 
above. 

4. Wilt, Root Rots, Stem or Crown Rots, Southern Blight, Dam ping-off — Leaves are 
stunted, yellowish, finally die. Stem base and roots decay; may be dry, mushy or 
slimy, and foul-smelling. Plants turn yellow, wilt, and gradually or suddenly die. 
Seedlings wilt and collapse. May be associated with root-feeding nematodes. Con- 
trol: Where practical, plant in light, well-drained soil which is sterilized. See "Soil 
Treatment Methods and Materials" in the Appendix. Avoid overwatering. Rotate. 
Treat seed with Semesan, captan, thiram, dichlone, or chloranil. 

5. Smuts — Leaves, stems, flowers, flower stalks, and seed may be infected. Large, 
elongated, dark purple blisters on the foliage which later burst open to release 
black, powdery masses. Petioles are deformed. Control: Dig up and burn infected 
plants when first found. Treat seed as for Wilt (above) or plant only disease-free 
stock. Practice rotation. 

6. Downy Mildew — Irregular, pale leaf spots with a light grayish-purple mold on the 
underleaf surface in damp weather. Leaves rot quickly in wet weather. Plants may 
droop and die without showing definite dead areas. Control: Same as for Anthrac- 
nose (above) . 

7. Rusts — General. Pale green spots on the upper leaf surface and yellow "cluster 
cups" on the corresponding underside. Rust also occurs on the swollen parts of 
veins, petioles, and stems. Later, the pustules turn light brown and finally dark 
brown or black. Flowering may be reduced. Alternate hosts: wild grasses 
(Andropogon) or none. Control: Same as for Anthracnose (above) . 

8. Oedema, Corky Scab — Indoor problem. Small, corky, or wartlike growths on the 
leaves and flower stalks. Affected plant parts become dry and brittle. Control: In- 
crease air circulation. Avoid overwatering. Lighten or cultivate the soil. Control 
insects with malathion sprays. 

9. Mosaics, Calico, Flower Breaking — Flower petals show white or light streaks or 
blotches. Flowers are often dwarfed and deformed. Leaves are slightly curled and 
yellowed, mottled green and yellow. See (16) Mosaic under General Diseases. 
Control: Buy virus-free plants or start from seed. Destroy infected plants when 



310 PAPAVER 

first found. Keep down weeds. Control aphids which transmit the viruses. Use mala- 
thion. 

10. Root Nematodes — Plants may appear unthrifty and sickly. Small wartlike galls 
on the roots (Root-knot) or sunken brown areas (Dagger, Lance, Root-lesion, 
Spiral, Stylet or Stunt) . Roots may be stunted, stubby, bushy, and decayed. Control: 
Set out disease-free plants in clean or sterilized soil (pages 437-44) . 

11. Curly-top — Western states. Shoots are stunted. Form rosettes. Flowers dwarfed and 
produce few seed. Control: Apply malathion and DDT to control leafhoppers 
which transmit the virus. Otherwise, same as for Mosaics (above) . 

12. Ringspot — Widespread. Numerous dead rings with green centers develop in the 
leaves. Control: Same as for Mosaics (above) . 

13. Aster Yellows — Plants stunted and bright yellow. Control: Same as for Curly-top 
(above) . 

14. Sooty Mold — Black, moldy patches on the leaves following insect attacks. Control: 
Spray with malathion when insects are first seen. 

15. Leaf Nematode — New leaves are dwarfed and distorted. Plants may not flower. 
Stalks are stunted. The base of the petiole may be swollen and irregular. Control: 
Move to a new bed. Start with new, disease-free plants. If you must use plants from 
the old, infested bed, first soak the plants in hot water (110° F.) for 30 minutes. 
Cool, then plant. 

PAPAVER -See Poppy 

PAPER-MULBERRY - See Fig 

PARKINSONIA - See Honeylocust 

PARIS DAISY -See Chrysanthemum 

PARSLEY -See Celery 

PARSNIP -See Carrot 

PARTHENOCISSUS - See Grape 

PARTRIDGE-BERRY - See Buttonbush 

PASQUEFLOWER - See Anemone 

PASSIONFLOWER (Passiflora) 

1. Leaf Spots — Spots of various sizes, shapes, and colors on the leaves. Spots may also 
occur on the fruit, causing shriveling. Control: Apply zineb, maneb, or fixed copper 
just before wet periods. Prune annually to thin out plants. 

2. Stem or Collar Rot, Southern Blight — Plants turn yellow and wilt from a rot at 
the soil line. Rot may be covered with a white mold growth. The bark rots, ex- 
posing the wood. Control: Remove and burn infected plants. Plant in well-drained 
soil which is near neutral (pH 7) . 

3. Gray-mold Blight — Plants may wilt and die. See under Begonia, and (5) Botrytis 
Blight under General Diseases. 

4. Root-knot — Southern states. Plants stunted and sickly, especially on sandy soils. 
See (37) Root-knot under General Diseases. 

5. Seedling Wilt, Anthracnose, Stem and Leaf S/>oi - Uncommon. Seedlings wilt and 
die. Control: Same as for Leaf Spots (above) . 

6. Root Rot — See (34) Root Rot under General Diseases. 



PEA 311 

PASTINACA-See Carrot 

PATIENCE PLANT -See Balsam 

PAULOWNIA, EMPRESSTREE, PRINCESSTREE (Paulownia) 

1. Leaf Spots — Spots occur on the leaves in rainy seasons. Control: Collect and burn 
fallen leaves. Where practical, spray several times during rainy periods, using zineb, 
maneb, or fixed copper. 

2. Wood Rot — See under Birch, and (23) Wood Rot under General Diseases. Con- 
trol: Avoid wounding the bark on the trunk. Paint wounds promptly with tree 
wound dressing (page 25) . Fertilize and water to maintain tree vigor. 

3. Root Rot — See (34) Root Rot under General Diseases. 

PAWPAW (Asimina); ROLUNIA 

1. Leaf Spots, Leaf Blotch — Widespread. Small to large, round to irregular spots and 
blotches of various colors on the leaves. Control: Collect and burn leaves in the 
fall. Prune to keep trees thinned out. If necessary, spray several times during rainy 
periods, 10 days apart. Try using zineb, maneb, or fixed copper. 

2. Twig and Branch Cankers, Diebacks — Twigs and branches die back due to dis- 
colored cankers. Control: Prune out and burn infected parts. Make cuts several 
inches beyond any sign of infection. See under Maple. 

3. Wood Rots — See under Birch, and (23) Wood Rot under General Diseases. 

4. Sooty Mold — Black, moldy patches on the leaves and twigs. Control: Apply mala- 
thion sprays to control insects. 

5. Fruit Rot — Fruits spotted, later rot. Control: Apply zineb or captan sprays during 
rainy periods as fruits are growing. 

PEA, GARDEN (Pisum); ROSARYPEA (Abrus); BUTTERFLY-PEA (Centrosema, 

Clitoria); CROWNVETCH (CorowUa); CROTALARIA; HYACINTH-BEAN, 

TWINFLOWER (Dolichos); SWEETPEA, EVERLASTING or PERENNIAL PEA, 

BEACH PEA (Lathyrus); LENTIL (Lens); LUPINE [ ANNUAL, BLUE, 

PERENNIAL, RUSSELL, SUNDIAL or QUAKER BONNETS, TEXAS or 

BLUEBONNET, YELLOW, WASHINGTON, and WHITE ] (Lupinus); SENSITIVE 

PLANT (Mimosa); BUSH-PEA, GLOWING GOLD, GOLDEN-PEA, 

AARONS-ROD (Thermopsis); VETCH (Vicia); ASPARAGUS-BEAN or 

YARDLONGBEAN (Vigna) 

1. Fusarium Wilt, Near Wilt, Root Rot — Widespread in northern states, especially on 
garden pea. Caused by two races of the same or closely related fungi. Yellowish, 
dwarfed plants which often wilt and die starting with the lower leaves at about 
blossoming time. Leaflets are small, rolled, and distorted. Plants may break over 
near the soil line. Yellow-orange to a brownish-black (Pea Wilt) or brick-red 
(Near Wilt) streaks inside the lower part of the stem. Wilt often occurs in patches. 
Pods normally do not form. Roots decay. Seedlings damp-off. Often associated with 
nematodes. Control: Avoid overfertilization and overcrowding. Treat seed as for 
Seed Rot (below) . Rotate 4 years or more. If practical, plant in sterilized 
soil (see pages 437-44 in the Appendix) or drench soil for flowers using a 1:2,000 
solution of mercuric chloride (1 pint to 5 feet of row) . Plant wilt-resistant pea 
varieties, where adapted: Ace, Alaska W.R., Alcross, Alderman, Apex, Bruce, Can- 
ner, Climax, Delwiche Commando, Dwarf Alderman, Early Harvest, Early Perfec- 
tion W.R., Early Sweet 11, Eureka, Extra Early, Freezer 37, Freezonian, Glacier, 
Green Giant, Hardy, Horal, Improved Gradus, Jade, King, Laxton 7, Lax ton's 



312 PEA 

Progress, Lola, Midfreezer Emerald, Morse Market, New Era, New Season, New 
Wales, Pacemaker W.R., Pacific Market 40, Penin, Pride, Profusion, Ranier, Re- 
sistant Early Perfection 326, Resistant Surprise, Shasta, Small Sieve Freezer, Stratage 
M, Surpass, Teton, Thomas Laxton W.R. or 251, Wisconsin Early Sweet, Wisconsin 
Merit, Wyola, and Yellow or Green Admiral. Plant in well-drained soil. Pea varie- 
ties normally resistant to Near Wilt: Delwiche Commando, New Era, New Season, 
New Wales, Horal, Horsford, and Rogers 95. 

2. Root Rots, Foot Rots, Southern Blight, Crown Rots, Stem Canker — General and 
serious in wet weather. Seeds rot. Stand is poor. Seedlings sickly, shrivel, and die. 
Older plants often sickly, stunted, and yellow. May collapse. Plants may wilt and 
die at or near flowering time. Crown and roots are discolored and rotted. May be 
covered with mold growth. Often occurs in patches which gradually enlarge during 
the season. Plants are easily pulled up. Often associated with Fusarium Wilt or 
Near Wilt, Seed Rot, and Nematodes. See Figure 47D. Control: Treat seed as for 
Seed Rot (below) . Plant early in a fertile, well-drained soil. Four- to 6-year rotation. 
Avoid close and deep cultivating. Keep plants growing vigorously. If practical, dig 
up and burn infected plants. Pea varieties which are somewhat resistant to Fusa- 
rium or Aphanomyces Root Rots: Acquisition, Green Admiral, Freezonian, Horal, 
Pacific Freezer, Premier Gem, Rice No. 300, Resistant Thomas Laxton 251, Sel- 
kirk, Sutton's Ideal, Wando, and World's Record. For flowers, drench the soil 
with mercuric chloride (see Fusarium Wilt, above) or plant in sterilized soil. 

3. Powdery Mildews — General. White to gray powdery coating on the leaves, pods, 
and stems. Leaves may turn yellow, wither, and die. Plants may be dwarfed. See 
Figure 148B. Control: Plant plump, disease-free seed. Apply sulfur or Kara thane 
several times, a week apart. Do not apply when the temperature is over 80° F. or 
when plants are in flower. Rotate. Increase air circulation and keep water off the 
foliage. Space plants. Resistant pea varieties may be available soon. 

4. Seed Rot, Damping-off — General. Seeds rot. Seedlings sickly, wilt, and collapse. 
Stand is thinned. Control: Treat sweetpea seed by soaking 1 minute in alcohol 
followed by a 20-minute soak in a 1:1,000 solution of mercuric chloride. Wash 
treated seed in running tap water for 3 to 5 minutes. Dry and dust as for other 
seed. Treat othei seed with thiram, captan, dichlone, or Semesan. Avoid deep plant- 
ing and poorly drained soil. If damping-off starts, apply the Shot-gun Soil Drench 
(page 92) . 

5. Bacterial Leaf Spots and Blights — General. Small to large, dark green, water-soaked 
spots on the pods, petioles, stem, leaves, and blossoms. Spots later dry up and turn 
yellow or brown. Flowers are killed or young pods shrivel. Pods may appear scalded 
and cracked. Branches or entire plants may wilt and die. Often follows strong 
winds, late spring frosts, or hail. Control: Plant disease-free seed grown in western 
states. Treat seed as for Seed Rot (above) . Rotate at least 2 years. Keep down 
weeds. Do not work among wet plants. Plant early in well-drained soil. 

6. Virus Complex (mosaics, streaks, stunt, mottle, wilt) — General. Symptoms change 
with the plant, variety, viruses involved, age of plants, weather conditions, and 
other factors. Leaves generally mottled (lightly to severely) or spotted with a 
yellow, light green, and dark green mosaic pattern. Plants may be dwarfed and 
yellowish with crinkled, curled, and distorted leaves and pods. Light brown, red- 
dish-brown, or purplish streaks may develop on the stem and petioles (Streak) . 
Young shoots may be stunted and "bushy." Plants may wilt, even die. Flowers 
often "broken" with white streaks and blotches. Pea pods may be spotted, dis- 
torted, twisted, roughened, or few in number. Seed formation is often abortive. 
See Figure 148. Control: Keep down weeds. Use malathion at least weekly to con- 
trol aphids and other insects which transmit the viruses. Plant seed from virus-free 



PEA 



313 



HEALTHY 



Fig. 148. A. Mosaic of sweetpea, leaves, 

B. Powdery mildew of sweetpea, C. 

Mosaic or flower breaking. 




plants as early as possible. Destroy infected plants when first found. Burn plant 
refuse after harvest. Pea varieties resistant to one or more viruses: Horal, Hundred- 
fold, Little Marvel, Morse Market, New Era, New Season, New Wales, Pride, Re- 
sistant Surprise, Wisconsin Early Sweet, and Wisconsin Perfection. 

7. Spotted Wilt, Ringspot — Yellow, brown, or purple rings, often zoned, or small, 
round, brown, or purple spots on the leaves. Leaves may be somewhat mottled, dis- 
torted, and misshapen. Discolored, circular patterns may appear on the flowers. 
Control: Control thrips which transmit the virus. Use DDT and malathion. Destroy 
infected plants. Keep down weeds. 

8. Ascochyta and Mycosphaerella Blights, Stem Rot, Foot Rot, Leaf and Pod Spot — 
General in wet seasons. Light brown, dark brown, black, or purplish streaks on the 
stem. Stems may be darkened and girdled, killing the portions beyond. Leaf spots 
are round to irregular with light or dark centers and darker margins. Spots may 
run together forming brownish-purple blotches. Black dots may be sprinkled in 
diseased areas. Sunken spots occur on the pods. Young pods may be distorted and 
wither. Control: Plant large, plump, disease-free seed, grown in western states, in 
well-drained soil. Treat seed as for Seed Rot (above) . Three- to 5-year rotation. 
Destroy plant debris after harvest. Burn or bury deeply. Keep down weeds. The 
pea variety Perfection (Advancer) has some resistance. Avoid overwatering. Spray 
sweetpeas with ferbam, zineb, or captan. 

9. Downy Mildew — General. Irregular, water-soaked, yellow to brown blotches on 
the upper leaf surface and white, light violet, grayish-brown, or almost black mold 
growth on the underleaf surface. Leaves curl downward, gradually wither and die. 
Yellowish spots on pea pods which are filled with mealy, white mold growth. Pods 
are distorted with spots turning dark brown. Young plants are very susceptible. 
Stems may be killed. Control: Plant disease-free seed grown in western states. Four- 
year rotation. Keep down weeds. Plant in well-drained soil. Destroy plant debris 
after harvest. Apply zineb, maneb, or fixed copper, plus spreader-sticker, weekly 
during cool, wet periods. 

10. Septoria Blight, Leaf Spot or Blotch — Widespread but infrequent. Yellowish spots 
at the margins of leaves which later enlarge and turn brown. Centers may later be 
sprinkled with black dots. Leaves often wither and die. Young plants may die. 



314 PEA 

Control: Same as for Downy Mildew (above) . Pea varieties (e.g., Perfection) have 
some resistance. 

11. Anthracnose , Leaf and Pod Spot — Widespread and serious. White or gray to 
brown sunken spots with dark margins on leaves, pods, flowers, and stems. Spots 
may enlarge and leaves wilt, wither, and fall early. Commonly follows Ascochyta 
Blights. Shoots and flower stalks may wilt and wither starting at the tips. Drying 
pods blanch and shrivel. Control: Same as for Ascochyta Blights (above) . Spray 
as for Downy Mildew (above) . Captan or ferbam may also be used. Fertilize and 
water to keep plants growing vigorously. Do not plant near apple or privet. 

12. R usts — Unimportant. Small, cinnamon-brown to dark brown, dusty pustules on 
the leaves. Mostly on the underleaf surface. Causes decreased vigor. See (8) Rust 
under General Diseases. Pea varieties differ in resistance. Late-maturing varieties 
are more commonly infected. Alternate hosts may include spurge (Euphorbia) and 
wheatgrass (Andropogon). 

13. Fasciation, Leafy Gall, Crown Gall — Primarily a disease of sweetpea. Very short, 
thick, strap-shaped, fleshy stems (witches'-brooms) develop near the soil which 
form distorted and misshapen leaves. Plants are stunted. Blossoming and fruit 
set is reduced. See Figure 42A under General Diseases. Control: Plant disease-free 
seed in clean or sterilized soil (pages 437-44) . Treat soil for sweetpea as for 
Fusarium Wilt (above) . Treat seed as for Seed Rot (above) . 

14. Root-knot, Cyst Nematodes — Southern states and indoors in the north. Oval or 
elongated galls and cysts formed along the roots. Plants are stunted, yellowish, 
and grow slowly. Varieties differ in resistance. Check with your extension horticul- 
turist or plant pathologist. See (37) Root-knot under General Diseases. 

15. Gray-mold Blight, Blossom and Shoot Blight, Pod Rot — General on sweetpea. 
Flowers spotted and rot in damp weather. Brown blotches develop on leaves and 
pods. Base of stem may rot causing plants to wilt and die. A gray mold may grow 
on affected areas in damp weather. Control: Same as for Downy Mildew (above) . 

16. Other Leaf Spots and Blights, Pod Spots, Scab — Spots of various sizes, shapes, and 
colors on the leaves. Leaves may be stunted and distorted or wither and drop off. 
May start at the base of the plant and progress upwards. Pods may be spotted and 
distorted. May be covered with mold growth. Control: Pick off and burn affected 
leaves. Plant disease-free seed in clean or sterilized soil. Dust or spray as for Downy 
Mildew (above) starting about 3 weeks before leaf spot usually appears. Rotate. 
Pea varieties differ in resistance. Indoors, lower the humidity and keep water off 
the foliage. Space plants. 

17. Verticillium Wilt — Brown discoloration inside the stem near the soil line. See 
(15B) Verticillium Wilt under General Diseases. 

18. Bud Drop (sweetpea) —Young flower buds turn yellow and drop instead of open- 
ing. Primarily an indoor problem. Control: Provide extra light during overcast 
weather. Avoid overwatering and overfeeding with a fertilizer high in nitrogen. 
Use a balanced fertilizer based on a soil test. 

19. Bacterial Wilt — See (15C) Bacterial Wilt under General Diseases. 

20. Black Walnut Injury — Plants growing under black walnut trees wilt and die. Con- 
trol: Do not grow plants within 50 feet of these trees. 

21. Other Root-feeding Nematodes (dagger, lance, naccobus, pin, reniform, ring, root- 
lesion, spiral, stem, sting, stubby-root, stylet or stunt) — Mostly southern states. 
May be associated with sickly, stunted plants. Control: Same as for Root-knot 
(above) . 



PEACH 315 

22. Leaf Nematode (lupine) — See (20) Leaf Nematode under General Diseases. 

23. Seed Smut (lupine) — See (11) Smut under General Diseases. 

24. Black Mildew (dolichos) —See (12) Sooty Mold under General Diseases. 

25. Chlorosis — Manganese, copper, or zinc deficiency. Have a soil test made and follow 
the instructions in the report. 

PEACH [COMMON, CHINESE WILD or DAVID, DOUBLE (WHITE-FLOWERED, 
PINK-FLOWERED, RED-FLOWERED), FLOWERING], APRICOT [COMMON, 
DWARF FLOWERING, FLOWERING, JAPANESE], NECTARINE, ALMOND 

[ DWARF FLOWERING (PINK and WHITE), FLOWERING, PINK, 

RUSSIAN], PLUM [ALLEGHENY, AMERICAN (PURPLELEAF), BEACH or 

BLACK, CANADA, DAMSON TYPE or BULLACE, GARDEN or PRUNE, 

JAPANESE, MYROBALAN or CHERRY, PACIFIC, PURPLE or ORIENTAL, 

WILD GOOSE, BLACKTHORN], PURPLELEAF BUSH, CHERRY-LAUREL 

[CAROLINA, ENGLISH], CHERRY [ BESSEY (HANSENS-BUSH or WESTERN 

SAND), BLACK, BITTER, BUSH, CATALINA ISLAND, CHINESE BUSH, 

DOUBLE-FLOWERED SOUR, DOUBLE-FLOWERED MAZZARD, FUJI, HIGAN, 

HOLLYLEAF, HYBRID BUSH, JAPANESE FLOWERING, EUROPEAN BIRD, 

NANKING or MANCHU, NADEN, NANKING BUSH, ORIENTAL FLOWERING 

(KWANZAN, SHIROFUGEN, AMANOGAWA, FUGENZO, KIKU-SHIDARE, 
SHIROTAE OR MOUNT FUJI, TEMARI), MAHALEB or ST. LUCIE, MORELLO, 
PURPLELEAF SAND, SAND, SARGENT'S JAPANESE, SOUR (DWARF or PIE), 

SWEET or MAZZARD, WEEPING HIGAN, WILD RED or PIN, YOSHINO], 
ROSE TREE OF CHINA, MAYDAY-TREE, AMUR CHOKECHERRY, PURPLELEAF 

CHOKECHERRY (Prunus) 

I.Brown Rots, Twig Blights, Blossom Blights — General and serious. Blossoms wilt, 
turn brown, and rot in wet weather. Leaves on twig tips suddenly wither and turn 
brown. Twigs may die back. Soft, brown, rotted areas in the fruit. Affected areas 
may later be covered by tufts of gray to tan mold. Fruits shrivel and become dry, 
hard, wrinkled mummies. See Figure 46D under General Diseases. Control: Destroy 
wild or neglected stone fruits and other Prunus species nearby. Remove and destroy 
blighted twigs when first found. Avoid heavy dense growth and crowding of trees. 
Collect and destroy rotting fruit promptly. Handle fruit carefully. Dip picked fruit 
in a captan solution (2 tablespoons in a gallon of water) and refrigerate promptly. 
Follow the regular spray program (see Table 10 in the Appendix) using captan, 
thiram, sulfur, or maneb. Red Gold peach; Lexington and Redbud nectarines; 
Hemskirke, Moorpark, Tilton, and Wenatchee apricots have resistance. Control 
insects (e.g., plant bugs, plum curculio, oriental fruit moth) which provide wounds 
through which brown rot fungi enter. 

2. Twig, Branch and Trunk Cankers, Dieback, Gummosis — Widespread, may be 
serious. Discolored, slightly sunken, brownish areas on the twigs, branches, and 
trunk which enlarge and may girdle affected parts. Gum may exude from cankers. 
Buds are often killed. Twigs, branches, or entire trees, decline, wilt, and die back. 
See Figure 149. Control: Remove and burn all dead or dying twigs and limbs 
during late winter. Avoid excessively high fertilization, especially with nitrogen, in 
the fall. Protect trees against Winter Injury (see below) , borers, scales, and other 
insects, and cultivation or mowing wounds. Destroy severely infected trees. Cut away 
affected bark and wood on large cankers (see page 24) during the dormant period, 
and paint wounds with a water-asphalt emulsion containing 5 tablespoons per 
gallon of Elgetol or Krenite, or use a 1:500 solution of mercuric chloride (2 tablets 



316 



PEACH 




Fig. 149. Peach twig cankers. 



in 1/2 pint of water and i/ 2 pint of glycerine) . Follow the recommended spray pro- 
grams as for Brown Rots (above) and Scab (below) . Varieties differ in resistance. 
Apply dichlone, zineb, or maneb before leaf fall and after harvest. 
Wood Rots — Cosmopolitan. Stone fruits are very susceptible. Often follows freez- 
ing, insect damage, untreated pruning cuts, or other injury. See under Birch, and 
(23) Wood Rot under General Diseases. Control: Follow the recommended spray 
program in the Appendix (Table 10) . Control borers by spraying the trunk and 
scaffold limbs with DDT. Check with your county agent or extension entomologist 
regarding rate to use and dates of application for your area. 

Leaf Curl, Witches' -broom, Plum Pockets — General following cool, rainy weather 
in the spring. Unfolding leaves may become severely curled, "blistered," swollen, 
yellow, reddish or purplish, and leathery. Affected leaves wither and fall with a 
second crop of leaves forming later in the season. Severe attacks weaken trees and 
greatly reduce fruiting. See Figure 24 under General Diseases. On cherries, plums 
and cherry-laurel — closely grouped clusters of long, slender, irregular twigs arise 
near the same point on a stem (Witches'-broom) . Branches may be stunted. Twigs 
die back. Also on plums, extremely large, light-colored, hollow, wrinkled fruit which 
drop early (Plum Pockets) . Infected shoots are often distorted and swollen, later 
die. Control: Follow the spray program given in Table 10 in the Appendix. Prune 
out witches'-brooms. Destroy infected fruit. Maintain trees in a healthy, vigorous 
condition. Varieties differ in resistance. Apply a single dormant spray before buds 
swell in early spring using lime-sulfur (1:16), bordeaux (4-4-50), phenyl mercury, 
thiram, or captan. Follow the manufacturer's directions. Add a spreader-sticker 
to the spray to ensure wetting of the buds. 



PEACH 



317 



5. Cherry Leaf Spot, Shot-hole, Yellow Leaf — General and serious. Small, round, 
purplish to brown spots on the leaves which often cause severe early leaf yellow- 
ing and dropping. Spots may drop out leaving shot-holes. Fruit may fall pre- 
maturely. Repeated leaf loss weakens or kills trees. See Figure 18 under General 
Diseases and Figure 150. Control: Collect and burn fallen leaves in autumn. Follow 
the spray program outlined in the Appendix using captan, thiram, ferbam and 
glyodin, maneb, ziram, or sulfur. Cyprex (dodine) and Acti-dione are used by com- 
mercial growers and nurserymen. 

6. Black Knot (primarily cherry, plum, Mayday-tree, and apricot) — Widespread, 
especially in the eastern half of the United States. Elongated, rough, black swellings 
on the twigs, small branches, and even the trunk. Knots are a velvety olive-green 
color in the spring. Gradually become hard, brittle, and black by fall. Affected 
parts may die back. Trees gradually die. See Figure 41 under General Diseases. 
Control: Prune or remove infected wood in late winter. Make pruning cuts at 
least 3 to 4 inches below any sign of obvious infection. The painting of wounds on 
large limbs with Acti-dione (200 parts per million) is recommended. Follow the 
spray program given in the Appendix. Apply a delayed dormant spray of zineb, 
thiram (Thylate) , sulfur, or captan. Destroy wild or neglected plums and cherries. 



Fig. 150. Cherry leaf spot. 




318 PEACH 

7. Scab, Fruit Freckle — General. Small, round, dark olive-green or black spots on the 
fruit. If numerous, fruit may crack open. Yellowish-brown blotches with gray or 
bluish borders develop on the twigs. Twigs may die back. Leaves are spotted a dark 
green to brown and drop early. Spots may first drop out leaving shot-holes. Almond 
shoots turn brown. The leaves blacken and drop early. See Figure 28B and Figure 
18 Shot-hole under General Diseases. Control: Destroy nearby, neglected trees. A 
dormant spray on peach of phenyl mercury has given excellent control. Prune 
out and burn blighted twigs before growth starts. Apply sulfur, captan or ziram, 
at 10- to 14-day intervals, starting 10 days after bloom, following the spray program 
in Table 10 of the Appendix. 

8. Bacterial Cankers, Gummosis, Bacterial Spot, Shot-hole — General and destructive. 
Symptoms variable. Round to elongated, water-soaked, rough, raised, thick-edged 
cankers on the trunk, branches, and twigs. Diseased bark is brown, gummy, and 
often sour-smelling. Twigs and branches are girdled and die back. Dormant buds 
and blossoms are blighted, and there are sunken, black spots on the fruit. Fruit 
may become roughened with cracked, sunken spots. Small purple, reddish, or 
brownish spots on the leaves later drop out leaving shot-holes. Leaves often turn 
yellow and drop early, weakening the trees. See Figure 18 under General Diseases. 
Control: Plant healthy, vigorous trees in fertile soil where Bacterial Canker has 
not been present for a number of years. Keep trees vigorous by proper fertilization, 
cultivation, and pruning. Apply 2 or 3 sprays of bordeaux after harvest and before 
the leaves fall. Follow the spray program as for Brown Rot and Scab (both above) . 
Varieties differ in resistance (e.g., Hiley Ranger and Belle of Georgia peaches: 
Plums on Myrobalan rootstock) . Check with your local nurseryman, extension hor- 
ticulturist, or plant pathologist. 

9. X-Disease, Yellow-red Disease (peach, nectarine, cherries, plums, apricot, almond) 
— Widespread. Symptoms variable due to the presence of many virus strains. 

Peach — Leaves appear normal in the spring for the first 6 to 7 weeks. Then 
they show irregular, pale green to dark brown, or yellow-red to purplish areas which 
may later drop out leaving ragged shot-holes. Leaves remain pale green to yellow- 
ish-red. Tips of leaves on most varieties bend downward and the margins roll up- 
ward. Older leaves drop early, except for tufts of young leaves at the tips. Fruits 
shrivel and usually drop early or ripen prematurely. Bitter to the taste. Trees tend 
to die back gradually. X-disease may be confused with severe nitrogen deficiency 
and arsenic toxicity. 

Sweet and Sour Cherry (little cherry, buckskin, wilt and decline) — Fruit 
distinctly small, poorly colored, and usually pointed. Foliage symptoms variable, 
depending on the virus strain, variety, rootstock, soil conditions, and other factors. 

On Mazzard rootstocks: Trees lack vigor, are dwarfed. Foliage is somewhat 
sparse. Leaves are light green, later bronze-colored, may be in rosettes. Fruits on 
affected branches are usually small, poorly flavored, dull reddish-pink, yellow, or 
nearly white. Symptoms become more pronounced in succeeding years. 

On Mahaleb rootstocks: Bearing trees often wilt and decline in vigor and fruit- 
fulness. Die after several years. Foliage may be sparse and retarded in growth with 
leaves smaller, lighter green, or yellowish and narrower than normal. Leaves may 
drop early. Roots are killed progressively from the tips to the trunk. Young trees 
may wilt and die in 1 to 2 years. 

Plum, Apricot — Most commercial varieties may be symptomless carriers. 

Control: Destroy wild cherries, especially chokecherries, plums, peaches, and 
other wild Prunus spp. within 500 feet and preferably 300 yards or further. Destroy 
infected trees when first found. Plant only certified, virus-free trees from a reputable 



PEACH 319 

nursery. Plant only trees which are standard, well-tested varieties in your area. 
Follow a complete spray program (Table 10 in the Appendix) . Control insects, 
especially leafhoppers, which transmit the viruses, using a combination of methoxy- 
chlor or DDT and malathion. 

There are well over 50 stone fruit diseases caused by viruses which have been 
reported in the United States. New ones are found every year while others are dis- 
covered as being strains of previously reported viruses. Scientists do not know at 
present the true status of all these viruses. Only the more important and better 
known diseases are discussed here. For more information read a book such as USD A 
Handbook No. 10, "Virus Diseases and Other Disorders with Viruslike Symptoms 
of Stone Fruits in North America." If you suspect a virus disease, contact your ex- 
tension or state plant pathologist. 

10. Little-Peach, Little-Plum (peach, plum, apricot) —Roughly the eastern half of the 
United States. 

Peach — Fruit stunted, ripen later than normal. Fruit are usually insipid. Young 
leaves at the tips of affected branches are crinkled. Trees often stunted and bushy 
with pale, yellowish leaves. Leaves first darker green and more leathery than 
normal. Bend inward toward the shoot. Short, bushy shoots with clusters of leaves 
arise from the base of affected limbs. 

Plums and Apricot — Symptoms on susceptible varieties are similar to peach 
but usually much milder. Many plums are symptomless carriers. Japanese or 
Oriental plums are very susceptible. 

Control: Same as for X-Disease (above) . 

11. Rosette (peach, plum, apricot, almond, cherry) —Eastern half of the United 
States. 

Peach — Symptoms variable. Young trees suddenly wilt and die. Compact 
rosettes, 2 to 3 inches long, composed of 200 to 400 dwarfed leaves, are conspicu- 
ous with abnormally long, straight leaves at the base of the shoots. Leaves turn 
yellow and drop in early summer. Trees usually bear no fruit and die within a 
year. 

Plums — Growth is stunted. Yellowish rosettes of mottled leaves are often 
formed. Marianna plum appears to be immune. Japanese and Damson plums are 
susceptible. 

Apricot — Symptoms variable. Trees markedly stunted. Leaves may have a 
yellowish tinge and show a mosaic mottling. Typical rosettes are formed. 

Almond, Cherries — Growth is stunted. Rosettes of yellowish-green leaves are 
formed. 

Control: Same as for X-Disease (above) . 

12. Peach Yellows (peach, nectarine, plums, apricot, almond) — General over much 
of the United States, especially in eastern states. Symptoms variable. 

Peach, Apricot and Almond — Leaves are pale green, yellow or yellowish-bronze 
in color. May be mottled dark and light green. Leaves curl, roll upward and in- 
ward. Drop early. Fruit ripen prematurely, often with reddish or purple blotches. 
Flavor is bitter or insipid. Reddish streaks may be seen in the fruit flesh. Clusters 
of thin, wiry, erect snoots with narrow, yellowish, red-spotted leaves are com- 
mon. Trees appear bushy and often die in 2 to 6 years. See Figure 34C under 
General Diseases. 

Plum — Certain Japanese varieties are symptomless carriers. Other plums show 
typical foliage symptoms, but are often milder than on peach. 

Control: Same as for X-Disease (above) . 

13. Sour Cherry Yellows (Montmorency, Early Richmond, and English Morello) — 
Widespread. Infects all Primus spp. Symptoms variable. Leaves on sour cherry are 



320 PEACH 

mottled green and yellow. Later the entire leaf usually turns yellow and drops 
early. Failure of fruit spur development and willowy-type growth with long bare 
spaces on the twigs are common symptoms. Yields may be reduced from 20 to 
70 per cent. Many ornamental, wild, and sweet cherries and other Prunus spp. 
are symptomless carriers. The virus may be a strain of Peach Ringspot. Control: 
Same as for X-Disease (above) . Destroy infected trees in young orchards. 

14. Ringspot Complex, Tatterleaf — Widespread on practically all Prunus spp. 
Symptoms variable. Many plants are symptomless carriers. Caused by a complex 
of many virus strains. 

Sweet Cherry — Pale green to yellow mottling, spots, ring, oakleaf, and brown 
line patterns may form on the leaves. Dead spots (which may drop out) often 
develop. Terminal shoot growth may die back. Symptoms tend to fade as the 
season progresses. 

Sour Cherry — Finely etched rings or lines may form a network on the leaves. 
Dead spots in the leaves often drop out giving a "tatterleaf" condition. Blossoms 
may be distorted and often do not set fruit. Trees may have a thin appearance. 
Ringspot is often accompanied by Yellows (above) . 

Plums — Symptoms are often absent or mild. Common in Japanese and garden 
plums. Rings and yellowish patterns or dead flecks and spots are produced on some 
varieties, especially during the acute stage of the disease. Spots may turn brown 
and drop out leaving shot-holes and tattered leaves. See Plum Decline (below) . 

Almond, Apricot — Most virus strains producing symptoms cause ringspots 
or yellowish oakleaf patterns. These are most severe during the first year of in- 
fection. 

Peach — Symptoms variable. Growth may be stunted. Twigs die back. Yellowish- 
green, yellow, or brown rings and spots or oakleaf patterns form on the leaves. 
The centers may drop out leaving shot-holes. Buds are often killed. Trees may 
appear to recover, show no further symptoms. 

Control: Same as for X-Disease (above) . Plant only standard, well-tested varie- 
ties adapted to your area. Destroy older plum trees showing evidence of decline. 

15. Plum Decline (Line Pattern, Ringspot, Tatterleaf, Prune Dwarf) —Widespread. 
A virus complex which probably infects most Prunus spp. Symptoms variable. Foli- 
age is discolored with spotting and localized killing (reddening, yellowing, line 
or oakleaf patterns, ringspots, tattered and strap leaves) , plus sparse foliage, 
witches'-brooms, and dieback of twigs and branches. Growth is reduced. Individual 
trees or some plum varieties decline in vigor and productivity. Leaf spots may 
turn brown and drop out leaving ragged and torn leaves. Common in Japanese 
and garden plums. Prune Dwarf is a strain of Peach Ringspot virus. Striking, 
yellow to white lines and oakleaf patterns develop on the leaves of Oriental flower- 
ing cherries. Control: Plant only virus-free trees of standard, well-tested varieties 
from a reputable nursery. Destroy older trees which show evidence of decline. 
Otherwise same as for X-Disease (above) . 

16. Phony Peach (peach, plums, apricot, almond) — Southern half of the United 
States, especially the eastern half. Flattened, abnormally dark green leaves. Termi- 
nal leaves are close together on stunted twigs. Fruit are small and ripen early. Poor 
in flavor. Growth is checked and trees are dwarfed. Fruit production stops after 
3 to 4 years. Twigs and branches die back. The causal virus is in practically all 
wild plums. Control: Same as for X-Disease (above) . Check with your county agent 
or extension plant pathologist. 

17. Mosaics (peach, nectarine, almond, apricot, plums, prune) — Southwestern half 
of the United States. Sweet and sour cherry and most cherry-like species are im- 
mune. Symptoms very variable due to many virus strains. 



PEACH 321 



Peach — The disease proceeds through acute and chronic phases. Severely in- 
fected trees later partially recover. Leaves may be crinkled and distorted with 
mottled, yellowish or yellowish-green spots, blotches, and irregular patterns. 
Clusters of twigs at the tips of branches. Leaves are often small and bunched in 
rosettes. Growth is retarded. Flowers are often streaked and spotted (broken) . 
Fruit may be misshapen, bumpy, and dwarfed with uneven color. Freestone varie- 
ties (e.g., Elberta, J. H. Hale) are most severely attacked. A few freestones, e.g., 
Erly-Red-Fre, Fisher, and Valiant are highly tolerant. Most clingstones (e.g., 
Paloro, Peak, Phillips, Sims) tolerate the virus with little damage. Check with 
your state or extension plant pathologist. 

Apricot, Almond and Other Hosts — Symptoms variable. Wild plums are usu- 
ally symptomless carriers. Leaves may be faintly mottled or sprinkled with indis- 
tinct to brilliant, lighter green spots or splotches, rings, or oakleaf patterns. Yel- 
lowish spots, stripes, and streaks may develop in the lighter green blotches. In- 
fected fruit may be bumpy, misshapen, and worthless. Stones of almond and apri- 
cot fruit show white rings and blotches. Some plum varieties are symptomless 
carriers. Others appear to be immune. 

Control: Same as for X-Disease (above) . Control bud mites and dagger nema- 
todes (Xiphinema) which help transmit certain viruses. Check with your extension 
entomologist. 

18. Apricot Ring Pox — Western states. Yellowish rings, mottling, or irregular blotches 
develop on the leaves. Later the leaves may be ragged with a shot-hole appearance. 
Irregular, reddish-brown blotches or rings appear on the fruit which may pit the 
surface causing distorted, bumpy fruit. Ripe fruit often crack in the discolored 
areas. Many affected fruit drop early. Control: Same as for X-Disease (above) . 

19. Cherry Rasp Leaf, Leaf Enation — Western states. Toothlike or rasplike out- 
growths (enations) protrude from the underleaf surface. Leaves may be smaller, 
narrower, markedly distorted, and longer than normal. Tree growth is stunted. 
Fruit crop is reduced. Control: Same as for X-Disease (above) . 

20. Cherry Mottle Complex (mild or severe mottle leaf; mild, severe and necrotic 
rusty mottle [ Lambert mottle ]) — Primarily in the Pacific Northwest. A complex 
of a number of virus strains. Symptoms are different depending on the variety, virus 
strain, and other factors. 

Sweet Cherry — Leaves on one or more branches, on certain varieties, show a 
variable, irregular, yellowish mottling. Leaves may be twisted, wrinkled, and 
puckered (Mottle Leaf) . Later, certain leaves may become bright yellow to red 
with islands of green (Rusty Mottle) . These leaves drop early. Mottling of the 
remaining foliage becomes more pronounced. The yellowish spots and areas may 
become yellowish-brown or brown and dead. The foliage from a distance has a 
general "rusty" or bronzed appearance. Where leaf drop has been heavy, the 
foliage is sparse except for the branch tips. In the fall, conspicuous dark green ring 
and line patterns develop on a background of yellow, brown, or brilliant red 
(Necrotic Rusty Mottle) . If severe, fruit may be small, hard, ripen late, and taste 
insipid. Trees may be stunted and appear rosette-like. Trees may die back and 
slowly decline. 

Sour and Oriental Flowering Cherries — May be practically symptomless carriers 
or show mild symptoms as for sweet cherry. 

Peach — Most varieties are symptomless. Certain varieties have leaves with 
striking greenish-yellow or yellow ringspots and patterns. Such leaves soon drop 
and the tree may appear normal. 

Control: Same as for X-Disease (above) . 

21. Asteroid Spot (peach, nectarine, almond, apricot, plums) —Widespread. Small, 
yellow, star-shaped areas develop along the veins of nearly full grown leaves. Large, 



322 PEACH 

angular blotches form along the veins on certain leaves. Leaves may then turn 
yellow with the flecks and splotches becoming light green. Such leaves drop early. 
Symptoms may only be evident during the acute stage. Apparently causes little 
damage. Control: Affected trees should be destroyed in the nursery and not used 
for propagating purposes. Control insects and mites by following the spray pro- 
gram in the Appendix (Table 10) . 

22. Cory neum Blight, Twig Canker, Shot-hole — Widespread. Most serious on peach 
and apricot. Small, round, reddish to purple spots on the twigs in early spring 
which may become brown, elongated, and slightly sunken. Twigs show gumming 
and dieback. Buds are darker in color and killed. Round, dark brown to reddish- 
brown leaf spots with dark red borders. Leaf spots may drop out leaving shot- 
holes. See (4) Shot-hole under General Diseases. Flowers may wither. Fruit spots 
are small, round, and a deep purplish-red. Later the spots become raised and 
roughened with the fruit cracking and exuding gum. Control: Follow the spray 
program in the Appendix. Apply one or more postharvest sprays of ziram, fixed 
copper, or bordeaux (5-5-50) . Check with your extension plant pathologist or hor- 
ticulturist. 

23. Verticillium Wilt, Blackheart Wilt — Mostly in western states. Symptoms variable. 
On peach the leaves on certain limbs are blanched, dull, and fall in early summer. 
Leaves on lower branches are attacked first as the disease progresses upwards. Gray 
or light to dark brown streaks are evident in the sapwood of infected trunk or 
limbs. Trees are stunted and may die gradually over a period of years or very 
suddenly (especially cherries) . On cherry the older leaves turn yellow and wilt 
in summer. Later the leaves turn reddish-violet with dry, curled margins and 
brown patches between the veins. Leaves turn yellow, quickly wilt and wither. 
Infected branches appear scorched with leaves remaining on the tree. Affected 
trees may live on for several years in a sickly condition with dead branches. Brown 
to black streaks in the sapwood. Control: Prune off and burn affected limbs at 
the trunk. Water and fertilize, where practical, to maintain good vigor. Destroy 
severely infected trees. 

24. Powdery Mildews — General. Young leaves tend to crinkle, twist, and fold up. They 
are covered with white to light gray powdery patches which may later become 
rusty-brown in color. Mold patches also develop on the young twigs and fruit. 
Fruit may be misshapen and "scabby." Most serious on young, rapidly growing 
trees. Control: If severe, apply sulfur or Karathane when first seen. Repeat in the 
next 2 regular sprays. Also apply a postharvest spray on cherries and apricots if 
mildew starts to build up. Varieties differ in resistance. 

25. Crown Gall, Hairy Root — General. Small to large, gall-like overgrowths on the 
roots and crown. Infected trees lack vigor and may die. Japanese apricot (P. mume) 
is resistant. Control: Plant disease-free nursery stock in soil which has not grown 
crown gall-infected plants for at least 3 years. Avoid wounding trees near the soil 
line. If galls are found on trees and disease has not progressed too far, paint the 
entire, intact gall and not more than \/ 2 inch beyond the gall, with the following 
mixture: To crystalline streptomycin (2,000 parts per million) or Terramycin (200 
parts per million) dissolved in a small amount of water (19 per cent) , add 20 per 
cent iso-amyl gradually, followed by kerosene (80 per cent) , melted lanolin (i/ 2 
per cent) , and Vaseline (i/ 2 P er cent) . Properly prepared, this mixture will be clear 
or slightly opalescent. Shake the mixture before using. Nurserymen soak plants 
for 10 to 30 minutes in Terramycin or Agrimycin 100 before planting. 

26. Rusts — General, especially in southern states. Small yellow spots on the upper leaf 
surface which become purplish or bronze in color. Leaves may drop early. Small, 
reddish, reddish-brown, dark brown or black dusty pustules form on the under- 



PEACH 323 



leaf surface. Round, sunken, green spots may develop on peach fruit. Control: 
Follow the spray program in the Appendix. Add zineb, ferbam, or sulfur to 
several consecutive sprays starting with the second cover. Some varieties may be 
susceptible to zineb injury. Destroy anemones, buttercup, hepatica, and meadow- 
rue, the alternate hosts. 

27. Root Rots, Crown Canker — Cosmopolitan. Trees lack vigor. Gradually die. 
Foliage remains stunted and sparse. Leaves often turn yellow and drop early. 
Toadstools may be evident at the base of a dying tree. Often in clusters. Usually 
associated with nematodes. Control: See under Apple, and Figure 47B under Gen- 
eral Diseases. Do not replant in the same soil without first fumigating with MC-2, 
or D-D. See pages 440-44 in the Appendix. Grow apricot on Myrobalan rootstock 
which is resistant to Armillaria Root Rot. Resistant rootstocks are also available 
for plums. 

28. Root-knot — Common in southern states, especially on sandy soils. Heavily infested 
trees are stunted, with light colored foliage. Trees gradually weaken due to small 
spindle-shaped or irregular "knots" on the roots. Fruiting is reduced. Control: 
Grow nematode-free, resistant rootstocks in soil which was fumigated before 
planting. Check with your nurseryman or extension plant pathologist. Nemagon 
and Fumazone have been used successfully around living trees. Follow the manu- 
facturer's directions. 

29. Other Root-feeding Nematodes (dagger, lance, needle, pin, ring, root-lesion, 
sheath, stem, sting, stubby-root, stunt or stylet) — General in the United States. 
Trees often stunted. Make poor growth. Do not respond normally to water and 
fertilization. Fruit production is decreased. Twigs and branches may die back due 
to small feeding roots being killed. This may result in small witches'-brooms, 
"brushes" of stubby roots, and brown rootlets. Control: Same as for Root-knot 
(above) . 

30. Minor Leaf Spots and Blotches, Leaf Blight, Shot-hole — General. Spots of various 
sizes, shapes, and colors on the leaves. Spots may later drop out. Spots often occur 
on the twigs. Control: Same as for Brown Rots (above) . Fertilize and prune trees 
to maintain vigor. 

31. Winter Injury (especially peach) —Twigs, limbs, or even whole trees may die 
due to freezing temperatures and low soil moisture. Affected wood is often dark. 
Foliage is off-color. Trees lack vigor. Control: Grow peaches where adapted. For a 
list of hardy varieties for your area check with local growers, your county agent, 
or your extension horticulturist. Varieties differ greatly in winter hardiness. 

32. Fruit Rots, Fly Speck — Cosmopolitan. See under Apple, and Brown Rots (above) . 
Tan, black, green, pink, bluish-green, or brown mold may grow on rotting fruit. 
Control: Same as for Brown Rots (above) . 

33. Sooty Mold — Cosmopolitan. See under Apple. Control: Follow the recommended 
spray program in the Appendix (Table 10) . 

34. Chlorosis, Little Leaf, Mottle Leaf — Leaves often pale and small. Yellowing 
varies from a complete lack of green color to light, yellowish-green areas between 
the veins. Veins usually remain green. Growth may be stunted and rosette-like 
(zinc deficiency) . Symptoms may appear first at the tips of the growing shoots 

where the leaves are yellowish (iron deficiency) . Leaves may drop beginning with 
those at the bases of the shoots and continuing out the shoots. If severe, twigs 
die back. This may be due to a lack of or unavailability of iron, manganese, mag- 
nesium, or zinc. Control: See under Maple for iron deficiency and under Walnut 
to control zinc deficiency. Have the soil tested. Check with a local grower, your 
county agent, or your extension horticulturist. To correct manganese and magne- 
sium deficiency check with your extension horticulturist. 



324 PEACH BELLS 

35. Wet Feet — Trees growing in excessively wet soils with a high water table are 
stunted with sparse foliage composed of dwarfed leaves, dead twigs, and branches. 
Leaves may turn yellow and drop early. Roots die back. Symptoms vary with the 
height and persistence of the high water level in the soil. Control: Drain the soil 

(page 25) or replant in a drier spot. 

36. Fire Blight (almond, apricot, cherry, cherry-laurel, flowering cherry, plums) — 
See under Apple, and (24) Fire Blight under General Diseases. 

37. Thread B Ugh t — Southeastern states. See under Walnut. 

38. Felt Fungus — Southern states on neglected trees. See under Hackberry. Control: 
Follow the recommended spray program (Table 10 in the Appendix) . 

39. Mistletoe — See (39) Mistletoe under General Diseases. 

PEACH BELLS -See Bellflower 
PEANUT (Arachis) 

1. Southern Blight, Stem Rots, White Mold, Root Rots or Soil R ot — Widespread in 
warm, moist weather. Entire plant or certain branches may wilt, wither, and die 
from a rotting of the lower stem, crown, and roots. Fruit stems (pegs) often de- 
cay. A white mold often occurs on infected parts under damp conditions. Control: 
Carefully dig up and burn infected plants. Cultivate shallowly and avoid throwing 
any soil on the crowns and lateral branches. Apply Terraclor (PCNB) as a dust 
or drench to the soil following the manufacturer's directions. Turn all plant debris 
under deeply (at least 4 inches) and cleanly several months before planting. Con- 
trol Leaf Spots. Keep down weeds. Three-year rotation. If using Terraclor, do 
not feed the vines as hay to livestock. 

2. Leaf Spots, Leaf Mold — General. Tan, brown, or black flecks, spots, or blotches on 
the leaves, often with light-colored margins. Elongated spots may occur on the 
petioles, stems, and pegs. Infected leaves usually turn yellow and drop early, reduc- 
ing the yield of nuts. Control: Apply sulfur, sulfur-copper mixture, zineb, or maneb 
three or four times at 10- to 14-day intervals. Start when the first spots appear on the 
older leaves. Rotate. 

3. Seed Rot, Seedling Blight — Seeds rot. Stand is thin. Seedlings are killed or weak- 
ened. Control: Plant high-quality, crack-free seed treated with thiram, Panogen, 
Ceresan, or chloranil. Plant in well-prepared soil which is 70° F. or higher. Avoid 
deep planting. 

4. Nematode Injury — Plants may be stunted with yellowish-green foliage. Tend to 
wilt during midday. Roots, fruit stems (pegs) , and fruit may have galls (Root-knot) 
or enlarged tap roots with a few short, stubby lateral roots (Sting Nematode) . 
Plants affected with meadow or root-lesion nematode have small brownish to black 
areas on the shell and lateral roots. Other nematodes include dagger, lance, pin, 
reniform, ring, spiral, stylet or stunt, and stubby-root. Control: Three-year ro- 
tation. Fumigate with D-D, DBCP (Nemagon or Fumazone) , Telone, or EDB 
about 3 weeks before planting, following the manufacturer's directions. Do not 
feed vines grown on fumigated soil to dairy animals or to animals to be slaughtered 
later for meat. 

5. Pod and Kernel Decays, Seed Molds, Concealed Damage — Cosmopolitan. Entire 
pod or kernel may become shriveled with the seed blackened and oily. Black, blue- 
green, green, white, or tan mold may grow on the pods and nuts. Pods and nuts 
may appear normal while nuts have an internal decay (Concealed Damage) . Con- 
trol: Follow the best cultural practices. See USDA Farmers' Bulletin No. 2063, 
Growing Peanuts. Apply gypsum (400 pounds per acre or about 10 pounds per 
1,000 square feet) , to plants after blooms appear. Apply in a wide band over the 



PEPEROMIA 325 



row for bunch peanuts and broadcast evenly for runner varieties. Keep plants 
growing vigorously until harvest. Control Leaf Spots, Stem Rot, and Nematodes (all 
above) and control leaf-feeding insects with DDT or methoxychlor. Harvest when 
the crop is mature (brown spots on the inside of the pods and a red color of the 
nut skin) . Allow vines to wilt thoroughly before curing artificially for several weeks 
at 90° F. or above on slats or stack poles. Hold vines at least 12 inches above the 
ground. Cover while curing to reduce weather and bird damage. Bunch and 
Spanish varieties are less subject to pod and nut decays than runner varieties. 

6. Rust — Uncommon. Southern states. Small, reddish-brown, dusty pustules on the 
leaves. Control: If severe enough, same as for Leaf Spots (above) . 

7. Bacterial Wilt — Uncommon. Southeastern states. See (15C) Bacterial Wilt under 
General Diseases. Peanut is quite resistant. 

8. Verticillium Wilt — New Mexico. Leaflets turn yellow, wither, and drop pre- 
maturely. Internal brown discoloration of the stem at or below the soil line. 
Control: See (15B) Verticillium Wilt under General Diseases. Bunch types are more 
resistant than Valencia and Spanish types. 

9. Mosaic, Stunt — Uncommon. See (16) Mosaic under General Diseases. 

10. Chlorosis, Manganese Deficiency — Occurs in neutral and alkaline soils. Plants are 
stunted. Leaves are yellowish between the veins. Control: Maintain the soil reaction 
(pH) between 5.7 and 6.2. Apply manganese sulfate to the soil with acid-forming 
fertilizers. On very acid soils (below pH 5.7) apply gypsum. See under Pod and 
Kernel Decays (above) . 

11. Hopperburn — Tips and margins of leaves are scorched. Leaves turn yellow. Plants 
are dwarfed. Yield of nuts and forage is reduced. Control: Apply DDT with Leaf 
Spot dusts or sprays to control leafhoppers. 

12. Thrips Injury — Seedling buds and leaves may be blackened. Leaflets are puckered 
and irregularly shaped with round to irregular, white spots on the surface. Seed- 
ling growth is delayed 2 to 3 weeks. Injury is most severe in dry weather. Control: 
Apply DDT when injury is first noticed. Repeat 7 to 10 days later. 

PEAR — See Apple 

PEARLEVERLASTING - See Chrysanthemum 

PEA-SHRUB, PEA-TREE -See Honeylocust 

PECAN -See Walnut 

PELARGONIUM - See Geranium 

PELLAEA-See Ferns 

PENSTEMON — See Snapdragon 

PEONY — See Delphinium 

PEPEROMIA 

1. Corky Scab — Indoor problem. Raised, copper-colored to dark, scablike growth on 
the underleaf surface. Control: Maintain as uniform a soil moisture supply as 
possible during moist, overcast weather. Increase air circulation. 

2. Ringspot — Distorted leaves showing zoned, yellowish or brown rings. Rings may 
fuse together forming irregular patterns. Leaves may be markedly cupped, curled, 
or twisted. Plants may be stunted. Control: Destroy infected plants. Take cuttings 
only from vigorous, virus-free plants. Root in a sterile medium. Control insects 
with malathion sprays. 



326 PEPPER 

3. Leaf Spots, Anthracnose — See under Calla. 

4. Stem and Root Rots, Cutting Rots — Plants stunted, gradually wither and die from 
a rotting of the stem at the soil line or below. May be associated with nematodes 
(e.g., burrowing, root-lesion, spiral) . Plant in well-drained soil which is clean or 

sterilized (pages 437-44) . Avoid overwatering. 

PEPPER -See Tomato 

PEPPERBUSH - See Sweet-pepperbush 

PEPPERGRASS - See Cabbage 

PEPPERMINT -See Salvia 

PEPPERTREE - See Sumac 

PEPPERVINE-See Grape 

PERENNIAL PEA -See Pea 

PERIWINKLE -See Vinca 

PERSEA — See Avocado 

PERUNKILA - See Oleander 

PERSIMMON [ AMERICAN or COMMON, JAPANESE, TEXAS or BLACK ] 

(Diospyros) 

1. Cephalosporium W ilt — Formerly common in the southern states on American or 
common persimmon. Leaves in the tops of trees suddenly turn yellow and wilt. 
Leaves drop later in the summer. Trees may be completely defoliated. Brownish- 
black streaks appear just under the bark when infected wood is cut. Affected trees 
soon die. Control: Japanese persimmons appear resistant. 

2. Wood Rots — See under Birch, and (23) Wood Rot under General Diseases. 

3. Twig Blights, Branch Canker, Dieback — See under Apple and Elm. 

4. Leaf Spots, Leaf Blotch, Tar Spot, Scab, Anthracnose — Spots and blotches of 
various colors, sizes, and shapes on the leaves. Affected leaves may wither and drop 
early. Certain organisms may also cause spotting of the fruit. Control: If serious 
enough, collect and burn fallen leaves. Spray as for Anthracnose of Maple or use 
ziram. 

5. Crown Gall — See under Apple, and (30) Crown Gall under General Diseases. 

6. Root Rots — Trees stunted and sickly with yellowish leaves. Tops die back. Roots 
discolored. See under Apple, and (34) Root Rot under General Diseases. May 
be associated with root-feeding nematodes (e.g., burrowing, citrus, stubby-root, 
trophotylenchulus) . 

7. Powdery Mildew — See under Birch, and (7) Powdery Mildew under General 
Diseases. 

8. Fruit Spots or Rots, Fly Speck — Rot spots of various sizes and colors on the fruit. 
May be covered with a black, blue, or gray mold in damp weather. Rots may de- 
velop in storage. Control: Check with your extension horticulturist, your extension 
plant pathologist, or a local grower. 

9. Root-knot — See under Peach, and (37) Root-knot under General Diseases. 

10. Verticillium Wilt — See (!5B) Verticillium Wilt under General Diseases. 

11. Thread Blight — Southeastern states. See under Walnut. 

12. Sooty Blotch — See under Apple, and (12) Sooty Mold under General Diseases. 

13. Mistletoe — See (39) Mistletoe under General Diseases. 



PHLOX 327 

PETROSELINUM-See Celery 

PE-TSAI — See Cabbage 

PETUNIA -See Tomato 

PHACELIA, SCORPIONWEED, CALIFORNIA-BLUEBELL (Phacelia); 
BABY-BLUE-EYES (Nemophila); ROMANZOFFIA 

1. Leaf Spots — Leaves variously spotted following rainy periods. Control: Pick off 
and burn spotted leaves. If needed, spray several times, 10 days apart, starting 
when the first spots are evident. Use zineb, captan, or maneb. 

2. Powdery Mildew (nemophila, phacelia) — Grayish-white, powdery mold on foliage. 
Control: Apply sulfur or Karathane twice, 10 days apart. 

3. Rusts (phacelia, romanzoffia) — Yellow-orange, reddish-brown, or black powdery 
pustules on the leaves. Alternate hosts: wild grasses, or none. Control: Same as for 
Leaf Spots (above) . Start spraying about 2 weeks before rust normally appears. 

4. Mosaic (phacelia) — Widespread. Leaves mottled light and dark green. Often mal- 
formed and distorted. Broad green bands develop along the leaf veins. Control: 
Keep down weeds. Destroy infected plants when first found. Control aphids which 
transmit the virus by spraying weekly with malathion or lindane. 

5. Curly-top (phacelia) —Western states. See (19) Curly-top under General Diseases. 

PHALAENOPSIS - See Orchids 

PHASEOLUS - See Bean 

PHILADELPHUS-See Hydrangea 

PHILIBERTIA-See Butterflyweed 

PHILODENDRON - See Calla 

PHLOX [ ANNUAL, CREEPING, DWARF, GROUND- or MOSS-PINK, WILD- 
SWEET-WILLIAM, HARDY or PERENNIAL, MEADOW, and THICK-LEAF] 
(Phlox); COLLOMIA; BLUE GILIA, SKYROCKET, TREE CYPRESS (Gilia); 
JACOBS-LADDER or GREEK VALERIAN (Polemonium); POLYGALA 

1. Powdery Mildews — General, especially where plants are shaded or crowded. Whit- 
ish, powdery mold patches on the upperside of leaves and stems from midsummer 
on. Leaves may shrivel and drop early. See Figure 21 D under General Diseases. 
Control: Space plants. Cut and burn all tops in the fall. Apply sulfur, Karathane, 
phaltan, or Acti-dione when mildew is first noticed. Repeat at 7- to 10-day inter- 
vals following the manufacturer's directions. Phlox varieties differ in resistance. 

2. Leaf Spots, Blights — General. Spots on the leaves of various sizes, shapes, and 
colors. Spots may run together forming irregular blotches. Usually occur first on 
the lower leaves which wither and dry up. Plants are stunted. Bloom is reduced. 
See Figure 17D under General Diseases. Control: Destroy tops in the fall. Apply a 
complete fertilizer in the spring. Plant disease-free seed treated with thiram, captan, 
or chloranil. Water during dry periods. Divide old clumps. Keep down weeds. 
Apply sulfur, zineb, ferbam, or fixed copper at 10-day intervals, starting a week 
before leaf spot is expected. Control insects and mites, using malathion. Phlox 
varieties differ in susceptibility. 



328 PHLOX 

3. Phlox Leaf Drop, Blight — Leaves turn brown and die progressively upwards from 
the base of the stem. Shoots may die. Most severe on older clumps where soil nutri- 
ents are exhausted. Varieties differ in susceptibility. Control: Same as for Leaf Spots 
(above) . 

4. Stem and Crown Rots, Southern Blight, Stem Blight or Canker, Root Rots — Gen- 
eral. Seedlings or older plants are often stunted, wilt, wither, and may collapse. 
Base of stem and roots are rotted. May be covered with a cottony mold. Control: 
Carefully dig up and destroy infected plants. Space plants. Three- or 4-year ro- 
tation. Avoid overwatering, overcrowding, and planting in heavy, poorly drained 
soil. When rot first strikes, soak base of plants with a 1:1,000 solution of mercuric 
chloride. Repeat in 2 weeks. Hill up fresh soil around infected plants. 

5. Mosaic — Widespread on phlox. Leaves are mottled light and dark green with 
some yellowing. Control: Destroy infected plants. Keep down weeds. Spray at 
weekly intervals with malathion to control aphids. 

6. Leaf and Stem Nematodes (collomia, ground- or moss-pink, phlox) — Plants may be 
stunted. Leaves are spindling, thickened, crinkled, or curled. Stems may be swollen 
or cracked and bent sideways near the tips. Buds swollen. Shoots are stunted, dis- 
torted, may die before producing flowers. Blotches on the leaves are caused by the 
Leaf Nematode. See under Chrysanthemum, and (20) Leaf Nematode under 
General Diseases. Control: Dig up and burn infested clumps when first found. 
Rotate plantings. Plant healthy seed or plants in soil fumigated with EDB, D-D, 
chloropicrin, or other fumigant. See "Soil Treatment Methods and Materials" in 
the Appendix. Varieties differ greatly in susceptibility. 

7. Aster Yellows — Flower petals often show white streaks and vein-banding. Clusters 
of flowers or individual petals may turn into green leafy structures. Successive 
flowers may develop from the ovaries. Control: Destroy infected plants. Keep down 
weeds. Spray weekly with a mixture of DDT and malathion. This controls the 
leafhoppers which transmit the virus. 

8. Fusarium and V erticillium Wilts — Stems on one side of the plant show wilting 
of the lower leaves. Wilt later progresses gradually up the stem. Control: Dig up 
and destroy infected plants. Rotate. Plant in well-drained soil. 

9. Downy Mildew — See (6) Downy Mildew under General Diseases. Control: Spray 
as for Leaf Spots (above) . 

10. Rusts — Yellow, orange, reddish-brown, or black pustules on the leaves. Control: 
Pick off and burn rusted leaves. Spray as for Leaf Spots (above) . Destroy tops in 
the fall. 

11. Root-Knot — See (37) Root-knot under General Diseases. 

12. Fasciation, Leafy Gall (phlox) —Uncommon. See under Pea, and (20) Leafy Gall 
under General Diseases. 

13. Gray-mold Blight — See under Chrysanthemum, and (5) Botrytis Blight under 
General Diseases. 

14. Crown Gall (phlox) — Uncommon. See (30) Crown Gall under General Diseases. 

15. Streak (phlox) —Streaks develop in leaves and stems. Leaf veins turn yellow. 
Later the petioles and leaves wither. Control: Dig up and burn infected plants. 

16. Chlorosis — See under Rose. 



PINCUSHION FLOWER 329 

PHOENIX -See Palms 

PHOENIX-TREE, CHINESE PARASOLTREE (Firmiana), CALIFORNIA 
FREMONTIA, FLANNEL-BUSH (Fremontia) 

1. Twig Canker, Coral Spot — Twigs and branches die back. Bark surface is cankered. 
May be covered with tiny, bright, coral-red "cushions." Control: Prune off dead 
and blighted twigs. Keep trees growing vigorously by fertilizing and watering dur- 
ing summer droughts. 

2. Web Blight — Southeastern states. See under Bean. 

3. Root Rot — See (34) Root Rot under General Diseases. 

4. Verticillium Wilt (fremontia) —See (15B) Verticillium Wilt Under General 
Diseases. 

5. Collar Rot, Stem Girdle (fremontia) — See under Dogwood. 

6. Leaf Spot — Unimportant. Leaves spotted. Control: Not necessary. 

PHOTINIA-See Apple 

PHYLA -See Lantana 

PHYSALIS-See Tomato 

PHYSOCARPUS - See Ninebark 

PHYSOSTEGIA - See Salvia 

PICEA-See Pine 

PIERIS — See Andromeda 

PIGGY-BACK PLANT, PICK-A-BACK PLANT (Tolmiea) 

1. Powdery Mildew — Grayish-white mold patches on the foliage. Control: Spray 
twice, 10 days apart, using sulfur or Karathane. 

PILEA — See Artillery-plant 

PIMPERNEL - See Primrose 

PIMPINELLA-See Celery 

PINCUSHION FLOWER -See Scabiosa 



330 



PINE 



PINE [ ALEPPO, AUSTRIAN, BLACK, CANARY, COMPACT MOUNTAIN, 

COLORADO, COULTER, HIMALAYAN, JACK or NORWAY, 

JAPANESE (BLACK, RED, UMBRELLA, WHITE), KOREAN, LACEBARK, 

LIMBER, MACEDONIAN, MUGHO, MOUNTAIN, PINYON, PITCH, 

PONDEROSA, RED, SCOTS or SCOTCH (PYRAMIDAL SCOTS), SWISS 

MOUNTAIN, SWISS STONE, VIRGINIA or SCRUB, WESTERN YELLOW, 

WHITE (DWARF PYRAMIDAL, UMBRELLA) ] (Pinus); FIR [ ALPINE, BALSAM 

or BALM OF GILEAD, CALIFORNIA RED, CILICIAN, COLORADO or WHITE, 

CONICAL, CORKBARK, GREEK, LOWLAND WHITE, MOMI, NIKKO, NOBLE, 

NORDMANN, NORMAN or CAUCASIAN, PACIFIC SILVER, 

ROCKY MOUNTAIN, SHASTA RED, SILVER, SOUTHERN BALSAM or 

FRASER, SPANISH, VEITCH ] (Abies); CEDAR [ ATLAS or ALGERIAN, BLUE 

ATLAS, DEODAR, CEDAR OF LEBANON, WEEPING BLUE ATLAS, WEEPING 

LEBANON ] (Cedrus); SPRUCE [ BLACK, BLACK HILLS, BLUE, COLORADO 

(BLUE, WEEPING BLUE), DRAGON, DWARF ALBERTA, DWARF ORIENTAL, 

DWARF SERBIAN, ENGELMANN, HEDGE-HOG, KOSTER'S, NORWAY 

(YELLOW, WEEPING), ORIENTAL, RED, SERBIAN, SITKA, TIGERTAIL, 

WESTERN WHITE, WHITE or CANADIAN, WILSON ] (Picea); 

DOUGLAS-FIR [ ROCKY MOUNTAIN, WEEPING ] (Pseudotsuga); 

UMBRELLA-PINE (Sciadopitys); REDWOOD, GIANT SEQUOIA (Sequoia); 

BALDCYPRESS (Taxodium); HEMLOCK [ CANADA or COMMON (DARK 

GREEN, WEEPING), CAROLINA, JAPANESE, MOUNTAIN, SIEBOLD, 

WESTERN] (Tsuga) 

I. Needle Casts, Leaf Blights, Tar Spots, Twig B Ugh ts — General, may be serious. 
Irregular, yellow, orange, reddish-brown, brown or black specks, spots, or bands 
on the needles. Needles later turn yellow, red, or brown, often from the tip 
downward, and drop prematurely. Twigs are stunted and may die back. Foliage 




Fig. 151. Pine needle blight. 



is sparse and trees appear sickly. See Figure 151. Growth slows down. The lower 
branches are usually attacked first. Trees may eventually die. Control: Collect and 
burn fallen needles. Prune out and burn dead twigs. Water during droughts. Ferti- 
lize trees in fall or early spring. Where practical, spray new growth when the 
"candles" are 14 emerged. Repeat 2, 4, and 6 weeks later, using zineb, maneb, 
phenyl mercury, fixed copper, or bordeaux mixture (4-4-50) plus wetting agent. 

2. Shoot or Tip Blights — New growth stunted. Wilts. Progressively turns pale green, 
then yellow, finally brown, and dies back. Twigs may die. Resembles spring frost 
injury. If severe, trees may be browned, stunted, and disfigured. Control: Same as 
for Needle Casts (above) . 

3. Wood and Heart Rots, Trunk Rot, Butt Rot — Cosmopolitan. See under Birch, 
and (23) Wood Rot under General Diseases. "Pecky cypress" is actually wood 
affected with a wood rot known as Brown Pocket Heart Rot. Wood-rotting fungi 
frequently enter through wounds made by insects. 



PINE 



331 



4. Twig, Branch, and Trunk Cankers — General. Oval to elongated, sunken or swollen, 
often flattened cankers with or without definite margins. Often found near branch 
stubs. Twigs and branches may be girdled and killed. Cankers later become rough 
and crack open. Resin streaks may flow from the wounds. Weakened trees, growing 
on a poor site, are most susceptible to infection. The lower branches often die 
first. Control: Remove and burn dead and dying branches. Avoid bark injuries. 
Paint over wounds promptly with tree wound dressing (page 25) . Increase vigor 
by fertilizing and watering. Spray as for Needle Casts (above) . 

5. Cytospora Canker, Twig Blight (primarily spruce, Douglas-fir, and hemlock) — 
Widespread and serious, especially on Norway and Colorado spruces. Koster's 
blue spruce and Douglas-fir are more resistant. Lower limbs turn brown and die 
back to the trunk. Later the disease progresses upward. Tufts of needles at the 
branch tips turn light gray or brown and die first. Large amounts of whitish resin 
are common on the dark bark of dying branches. More prevalent on trees older 
than 15 years. Control: None very satisfactory. Cut and burn dying branches and 
the two apparently healthy ones just above as soon as found. Do not prune when 
foliage is wet. Swab tools with 70 per cent denatured alcohol between cuts. Avoid 
injuring the bark. Otherwise same as for Twig, Branch, and Trunk Cankers 
(above) . 

6. White Pine Blister Rust (5-needle pines) — Widespread and serious, especially in 
forest plantings. Small, dark, oozing blisters on the twigs, branches, and trunk. 
Blister-cankers later form larger, bright orange to pale yellow, dusty pustules. See 
Figure 152. Disease spreads rapidly up and down the tree killing the branches. 



Fig. 152. White pine blister rust. (Iowa 
State University photo) 




332 



PINE 



Entire tree may die if the trunk is attacked and girdled. Alternate hosts include 
rust-spreading currants and gooseberries and Grossularia. Control: Promptly cut 
and burn affected parts. Make cuts at least 4 inches below the discolored bark at 
the edges of the canker. Increase this distance to 6 inches in the spring and early 
summer. Plant only currants and gooseberries from a reputable nursery. These will 
not become infected by the blister rust fungus. Destroy wild currants or goose- 
berries which are rust-infected. Paint or spray pines with a special formulation of 
Acti-dione in fuel oil. Follow the manufacturer's directions. 
7. Needle and Cone Rusts — Widespread but not serious. Whitish, yellow, reddish, or 
bright orange to brown, dusty pustules on the needles and cones. Needles often 




Fig. 154. Fusiform gall rust of pine. (Cour 
tesy Dr. V. H. Young 



turn yellow and may drop early. Most serious on young trees. May cause some 
distortion, dwarfing, and even death. See Figure 153. Alternate hosts include 
amsonia, apple, arborvitae, asters, azalea, blueberry, campanula, creeping snow- 
berry, crowberry, erigeron, ferns, fireweed, flowering currant, gayfeather, goldenrod, 
gooseberry, gumweed, heliopsis, huckleberry, hydrangea, iron weed, Jerusalem- 
artichoke, Labrador-tea, leatherleaf or cassandra, loosestrife, marigold, morning- 
glory, mountain-ash, poplars, pyrola, raspberry, rhododendron, silphium, sow-thistle, 
sunflower, sweetpotato, tickseed, venus-lookingglass, willow, and wood-nymph. Con- 
trol: If serious enough, spray as for Needle Casts (above) or use ferbam or sulfur. 
If practical, destroy nearby, worthless, alternate hosts (e.g., goldenrod, sowthistle) . 
Gall Rusts — More or less spherical, pear-shaped, or spindle-shaped galls (or large 
burls) on the branches or trunk up to a foot or more in diameter. Witches'-brooms 



PINE 333 

or deep cankers may form instead. Foliage beyond the canker or gall is discolored. 
Later wilts and dies. Seedlings and saplings are frequently killed. Galls appear 
whitish or yellow-orange and blister-like in the spring. See Figure 154. Oaks, chest- 
nut, sweetfern, sweetgale, Indian paintbrush, peregrina, lousewort, bastard toad- 
flax, birds-beak, owlclover, Pacific waxmyrtle, cow-wheat, and myriagale are the 
alternate hosts. Control: Where practical, remove the galls by annual pruning. De- 
stroy nearby worthless oaks and other alternate hosts. Plant rust-free nursery stock. 
Spray as for Needle Casts (above) or use ferbam or ziram (5 tablespoons per gallon 
of water) . 

9. Rust Witches' -brooms (fir, spruce) — Widespread. Young twigs are stunted from 
clusters of compact, broomlike growths with close clusters of dwarfed leaves. 
Needles may turn yellow and drop early leaving the bare witches'-brooms. The bark 
may show gall-like swellings. Orange blisters appear on the yellowish leaves later 
in the summer. Control: Where feasible, prune out and burn witches'-brooms. De- 
stroy the alternate hosts of fir rust: chickweed and stickwort (Stellaria). 

10. Seedling Blights, D ampin g-off , Root Rots — Cosmopolitan. Seedlings in nurseries 
wither, turn brown, and die. Roots decay. Plants are easily pulled up. Often associ- 
ated with root-feeding nematodes (see below) . Control: Treat seed with thiram, 
dichlone, or captan and plant in well-drained soil which has been treated with 
heat or chemicals. See pages 437-44 in the Appendix. Use a treatment which will 
kill weed seeds in the soil plus fungi and nematodes. Apply soil drenches of thiram, 
zineb, captan, maneb, or ferbam at monthly intervals from May to September. 
Use about 2 tablespoons of chemical per gallon of water. Apply about l/ 2 pint of 
solution per square foot. Keep down weeds. Avoid overwatering. 

11. Sooty Molds, Black Mildew — Widespread. Black mold growth on the needles and 
twigs. Often follows insect attacks. Control: Keep aphids, scales, and other insects 
in check by malathion sprays. 

12. Root Rots — Widespread. Trees decline in vigor. Foliage is thin and sickly. Needles 
turn yellow, wither, and drop early. Probably associated with root-feeding nema- 
todes. See under Apple, and (34) Root Rot under General Diseases. Control root- 
feeding insects and nematodes. Check with your extension entomologist. 

13. Root-feeding Nematodes (awl, cyst, cystoid, dagger, lance, needle, pin, ring, root- 
knot, root-lesion, sheath, spear, spiral, sting, stubby-root, stylet or stunt) — Plants 
grow more slowly. Tend to have poor color. Roots may die back. See under Root 
Rots (above) . Affected seedlings are stunted with smaller needles and poor color. 
Control: See under Peach, and (37) Root-knot under General Diseases. 

14. Witches' -broom, Dwarf and American Mistletoes — Primarily in western states. See 
Figure 52B, and (39) Mistletoe under General Diseases. 

15. Dieback — Tops of large trees turn yellow and die back, presumably because of poor 
growing conditions. Foliage thins. Leader growth and needles are stunted. Control: 
Water and fertilize trees to maintain good vigor. Mulch and water plants in late 
fall. Grow adapted species and varieties. Control insects with malathion sprays. 
Plant in well-drained soil. 

16. Winter Injury, Needle Scorch — Last year's needles turn reddish-brown and die 
from the tip down, usually more on exposed branches. Needles may fall during 
late spring or summer. Do not confuse with normal browning and falling which 
occurs late in the fall to the older needles or to those nearest the trunk. Control: 
Water plants late in the fall and during droughts. Mulch plants to prevent deep 
freezing plus alternate freezing and thawing (page 29) . Plant adapted and recom- 
mended species in a location protected from warm, dry, winter winds. 



334 PINK ALMOND 

17. Sunscorch and Wind Damage (primarily fir, hemlock, pine, and spruce) —Foliage 
appears scorched. Needles dry out and turn brown from the tip down. Tips of 
hemlock branches die back. Injury follows dry, windy weather with temperatures 
of 95° F. or higher. Severe winter weather and mite injury may cause similar 
symptoms. Control: Keep trees well watered during hot, dry periods. Plant in pro- 
tected locations. Control mites using malathion. 

18. Douglas-fir Bacterial Gall — California. Round, rough galls, up to several inches in 
diameter on the upper branches, twigs, or leader. Top may die. Control: Prune out 
galls. Control aphids, which spread the causal bacteria, with malathion sprays. 

19. Crown Gall (redwood) — See (30) Crown Gall under General Diseases. 

20. Brown Felt Blights, Snow Blights — Foliage is killed under the snow. Needles are 
brown and covered with white fungus growth as the snow melts (Snow Blight) or a 
dense brown to almost black, feltlike growth (Brown Felt Blight) . Black specks 
later appear on the needles. Control: Spray nursery beds and lowest branches on 
other trees with lime-sulfur (1:8) in late fall. 

PINK ALMOND -See Peach 

PINKS — See Carnation 

PINXTERBLOOM - See Rhododendron 

PIQUERIA — See Chrysanthemum 

PISTACHE, PISTACHIO (Pistacia) - See Sumac 

PISUM-See Pea 

PITTOSPORUM [ CAPE, JAPANESE ] (PiffosporumJ 

l.Leaf Spots — Small, angular, yellow to dull brown spots on the leaves. Leaves may 
turn yellow and drop early. Control: If practical, pick off and burn spotted leaves. 
Apply zineb, maneb, or fixed copper sprays at about 2-week intervals during rainy 
periods. 

2. Stem Rot, Southern Blight, Foot Rot — Plants wilt, wither, and die from a rotting 
of the stems near the soil line. Affected areas may be covered with white mold 
growth in damp weather. Roots may decay. Control: Plant in well-drained soil. 
Avoid wounding the bark. Keep trees growing vigorously. Avoid overwatering. 
Commercial nurserymen treat planting beds with steam or chemicals. See pages 
437-44 in the Appendix. Post-planting treatments may be beneficial. See under 
Cabbage Wirestem. 

3. Mosaic — See (16) Mosaic under General Diseases. 

4. Verticillium Wilt — See under Maple, and (15B) Verticillium Wilt under General 
Diseases. 

5. Root-knot — See under Peach, and (37) Root-knot under General Diseases. 

6. Thread Blight — Southeastern states. Plants may be defoliated early. See under 
Walnut. Control: Spray as for Leaf Spots (above) . 

PLANETREE (Platanus) — See Sycamore 

PLANTAINLILY - See Hosta 

PLATYCODON - See Bellflower 

PLUM -See Peach 



POINSETTIA 335 

PLUMARIS - See Carnation 

PLUMED THISTLE -See Chrysanthemum 

PLUME HYACINTH -See Tulip 

PLUMERIA-See Oleander 

PLUM -YEW — See Japanese Plum-yew 

PODOCARPUS - See Yew 

PODOPHYLLUM - See Mayapple 

PODRANAEA - See Catalpa 

POINCIANA - See Honeylocust 

POINSETTIA, SPURGE [CYPRESS, FLOWERING, PAINTED or 

MEXICAN FIRE -PLANT], SNOW - ON - THE - MOUNTAIN, 

CROWN-OF-THORNS (Euphorbia) 

Stem Rots, Foot Rots, Root Rots, Wilt — Serious indoor problem. Plants stunted, 
frequently decline and die. Cuttings (or stems) are rotted near the soil line. Cut- 
tings may fail to root. Stems, branches, and roots darken, eventually die. Leaves 
gradually wither, turn yellow, and drop off. This symptom is first noticeable at 
the base, from there it gradually covers the whole plant. Flowers are stunted, may 



Fig. 155. Poinsettia root rot (Thielaviopsis). 




HEALTHY 
i DISEASED 



be one-sided. See Figure 155. Control: Avoid overwatering, overcrowding, and 
splashing water on the foliage when sprinkling. Take tip cuttings from vigorous, 
disease-free plants. Dip in ferbam and root in light, well-drained, sterilized soil 
which is acid (pH 4.5 to 4.9) . Practice strict sanitation (e.g., use new pots or dis- 
infect old pots) . Indoors, maintain the recommended temperature at night and 
regulation of day length. If misting, reduce the mist period to 30 seconds and in- 
crease the no-mist period to \]/ 2 to 2 minutes. Check with your local florist or ex- 
tension horticulturist. Florists drench the cutting bed after cuttings are "stuck," 
using thiram, Semesan, or Pano-drench. Drench the soil monthly (1 quart per 
square foot) for three applications using a mixture of Terraclor plus ferbam. 
captan, thiram, or phaltan. Destroy severely infected plants. 



336 POKERPLANT 

2. Gray-mold Blight, Botrytis Tip Blight, Stem Canker — Flower clusters, especially on 
double varieties, and colored bracts are blasted and turn brown. Brown cankers 
form on the stem. A grayish mold grows over infected areas in cool, damp weather. 
Control: Indoors, space the plants, increase air circulation, and raise the temper- 
ature. Otherwise the same as for Stem Rots (above) . Maneb, zineb, or fixed copper 
sprays will often be beneficial. Carefully pick off and burn affected parts. 

3. Bacterial Canker and Leaf Spot, Bacterial Blight (poinsettia) — Long, narrow, 
dark, water-soaked streaks on the green stems and petioles. Stems may crack open 
and ooze. The growing point curves down and in. Light spots or blotches occur on 
the leaves which later turn brown. Infected leaves may drop early. Several branches 
may be completely blighted or the entire plant may die. Plants may show no 
symptoms for several months after becoming infected. Control: Same as for Stem 
Rots (above) . Avoid overfertilizing plants. Streptomycin sprays are beneficial. 

4. Crown Gall — Irregular galls at the base of plants. Control: Destroy infected plants. 
Root cuttings in sterilized soil (pages 437-44) . Avoid wounding plants. 

5. Chlorosis — Plants a sickly yellow. Lack vigor. Control: Plant in acid soil. Apply 
a complete fertilizer based on a soil test. 

6. Leaf and Stem Spots, Scab or Spot Anthracnose — Small spots on the leaves; 
sometimes on the stems. Young stems may die back. Leaves may drop prematurely. 
Control: Same as for Gray-mold Blight (above) . 

7. Rusts — See under Chrysanthemum. 

8. Root-knot — See (37) Root-knot under General Diseases. Plant growth is reduced. 

9. Powdery Mildew (snow-on-the-mountain, spurge) — See (7) Powdery Mildew under 
General Diseases. 

10. Stem Smut — (painted spurge) — Louisiana. See (11) Smut under General Diseases. 

POKERPLANT - See Redhot - pokerplant 

POLEMONIUM, POLYGALA-See Phlox 

POLIANTHES - See Daffodil 

POLYANTHUS - See Primrose 

POLYGONUM — See Silver Lacevine 

POLYPODIUM, POLYSTICHUM-See Ferns 

POMEGRANATE (Punica) 

1. Fruit Spots and Rots — Cosmopolitan. Rot spots develop in the fruit. Affected areas 
may be covered with a gray, blue, or black mold growth. See under Apple. 

2. Anthracnose, Spot Anthracnose, Leaf Blotch — See under Maple. 

3. Root-knot — See (37) Root-knot under General Diseases. 

4. Root Rot — See under Apple, and (34) Root Rot under General Diseases. 

5. Thread Blight — Southeastern states. See under Walnut. 

PONCIRUS-See Citrus 

PONDLILY-See Waterlily 

POND - SPICE - See Avocado 

POPCORN -See Corn 

POORMANS - ORCHID - See Tomato 



POPLAR 337 



POPLAR [ BALM - OF - GILEAD, BALSAM, BERLIN, BLACK, BOLLEANA or 

TURKESTAN, CAROLINA, CHINESE, COARSE - TOOTHED, GRAY, JAPANESE, 

KOREAN, LOMBARDY, MONGOLIAN, NORWAY, RIO GRANDE, SIMON, 

SILVER, WHITE], ASPEN [CHINESE, GOLDEN, JAPANESE, 

LARGE-TOOTHED, QUAKING or QUIVERLEAF], COTTONWOOD [BLACK 

or WESTERN BALSAM POPLAR, COMMON or NORTHERN, COTTONLESS, 

EASTERN, GREAT PLAINS, SOUTHERN, SWAMP ] (Populus) 

1. Twig, Branch, and Trunk Cankers, Dieback — General and serious. Rough, dis- 
colored, cracked, often sunken cankers on the twigs, branches, and trunk. Girdled 
parts cause the foliage beyond to die. Cankers may cause swellings on the trunk 
and formation of suckers on the trunk which become infected and die. The sap- 
wood under the cankers is discolored. Twigs and small branches die back first. Trees 
often die from the top down. Control: Use poplars best adapted to your area. 
Check with your extension horticulturist or nurseryman. Avoid wounding trees. 
Paint over wounds promptly with tree wound dressing. If practical, prune out all 
cankers on small branches. Disinfect cut surfaces with a 1:1,000 solution of mer- 
cury bichloride followed by tree paint. Lombardy, Bolleana, and Simon poplars 
are very susceptible to one or more cankers. Poplars and cottonwoods vary greatly 
in resistance. Certain cankers are so contagious that infected trees should be re- 
moved and burned. Water during droughts. Fertilize to maintain vigor. Sprays of 
fixed copper, zineb, or captan when applied at 2-week intervals, to nursery-size 
trees has proved beneficial. For additional information check with your extension 
horticulturist or plant pathologist. 

2. Leaf Spots, Leaf Blotch, Ink Spot — Common but not serious. Small to large, round 
to irregular leaf spots of various colors, often with dark margins. Spots often later 
enlarge. Leaves wither and fall early. Twigs may be killed back. Control: Collect 
and burn fallen leaves. If serious enough, apply two or three sprays, 10 days apart, 
starting when the buds break open, using phenyl mercury, zineb, fixed copper, 
or bordeaux (4-4-50) . 

3. Powdery Mildews — Widespread. White, powdery mold patches on the leaves. 
Control: If serious enough, spray several times, 10 days apart, using sulfur, Acti- 
dione, or Karathane. 

4. Leaf Rusts — General. Bright, yellowish-orange, dusty pustules, usually on the 
underleaf surface. Pustules may later turn reddish-brown to black. Leaves may fall 
early. Seldom causes serious damage. Control: Where practical, avoid planting 
near the alternate hosts: garlic, Douglas-fir, hemlock, bigcone spruce, and larch. 
If practical, apply zineb, maneb, dichlone, Acti-dione, ferbam, or sulfur two or 
three times, 10 days apart, starting a week before rust normally appears. 

5. Spring Leaf Fall, Scab, Shoot Blight — In late spring the tips of young leaves turn 
black. Affected areas enlarge, causing the leaves to blacken, wrinkle, wither, and 
drop by late spring. Shoots may be blighted causing loss of tree vigor. Control: 
Spray as for Leaf Spots (above) . Prune out and burn blighted shoots. Fertilize and 
water to maintain tree vigor. 

6. Wood Rots, Butt Rot — Cosmopolitan. See under Birch, and (23) Wood Rot under 
General Diseases. 

7. Yellow Leaf Blisters, Calkin Deformity — Widespread. Irregular, small to large, 
bright yellow to brown blisters on the leaves following cold, wet spring weather. 
Underleaf surface may show a bright golden "bloom." Catkins are deformed. Con- 
trol: If practical, apply fixed copper or ferbam before buds swell in early spring. 

8. Wetwood, Slime Flux — See under Elm. 



338 POPPY 

9. Branch Gall - Small, rounded galls up to H/ 2 inches in diameter, develop at the 
base of the twigs. Some twigs and small branches may die back. Control: Prune in- 
fected branches and dead twigs back several inches into healthy wood. Burn the 
prunings. 

10. Crown Gall — Also called Bacterial Limb Gall. Rough, irregular, swollen galls 
usually found at the base of the trunk or on the roots. Trees lack vigor. Make poor 
growth. Control: See under Apple, and (30) Crown Gall under General Diseases. 

11. Root R ots — Trees gradually decline in vigor. Foliage becomes thin and sickly. 
Leaves may turn yellow and drop early. May be associated with nematodes (e.g., 
ring, sheath) . See under Apple, and (34) Root Rot under General Diseases. 

12. Verticillium Wilt — See under Maple, and (15B) Verticillium Wilt under General 
Diseases. 

IS. Seed Rot, Damping-off — See under Pine. 

14. Mistletoe — See (39) Mistletoe under General Diseases. 

15. Chlorosis, Iron Deficiency — See under Maple. 

16. Sooty Mold — See (12) Sooty Mold under General Diseases. 

POPPY [ALPINE, CORN, ICELAND, ORIENTAL] (Papaver); 

PRICKLY - POPPY [ CRESTED, MEXICAN ] (Argemone); CELANDINE 

(Chelidonium); CALIFORNIA- POPPY (Eschscholtzia); TREEPOPPY 

or BUSHPOPPY (Dendromecon); MECONOPSIS, WELSH POPPY 

(Meconopsis); BLOODROOT (Sanguinaria) 

1. Bacterial Blight (poppy, California-poppy) —Small, water-soaked spots or blotches 
on the leaves, stems, flowers, seedpods, and roots. Spots soon turn black with a 
slimy exudate. Leaves may wither and drop early. Stems may be girdled, causing 
plants to die. Control: Cut off and burn severely infected parts. Pick off and burn 
spotted leaves on mildly infected plants. Plant seed from disease-free plants in 
clean or sterilized soil (pages 437-44) . Spray with a copper fungicide during wet 
weather. Streptomycin may also work. 

2. Stem and Root Rots, Damping-off — Seedlings sickly, wilt, and collapse. Older 
plants turn pale, wilt, and wither from a rot or canker of the lower stem or roots. 
Control: Plant disease-free plants or seed in clean or sterilized soil which is light 
and well-drained. Avoid overwatering, excessive use of fertilizers high in nitrogen, 
and wounding plants. Drench crown with a mixture of Terraclor plus captan or 
ferbam if suspicious (page 92) . Rotate. Spray as for Downy Mildew (below) . 
Treat seed of California-poppy by soaking in hot water (125° F.) for 30 minutes. 

3. Leaf and Seedpod Spots — Spots of various sizes, shapes, and colors on the leaves 
and seedpods. Leaves may die around blossom time. Control: Plant seed from dis- 
ease-free plants. Spray as for Downy Mildew (below) . Treat seed of California- 
poppy as for Stem and Root Rots (above) . 

4. Downy Mildew (poppy, prickly-poppy, meconopsis) — Seedlings blighted. May col- 
lapse and die. Yellowish or light brown spots and blotches develop on the upper 
leaf surface of older plants. The blotches later enlarge and become very dark. 
Spots on the underleaf surface are covered with white, grayish, or purplish mold 
in damp weather. Leaves may turn yellow, wither, and be deformed. Stems are dis- 
torted. Buds, flower parts, seeds, and capsules may also be infected. Plants may 
fail to bloom. Control: Destroy the first infected plants. Pick off and burn infected 
plant parts when they appear. Burn tops in the fall. Plant seed from disease-free 
plants in well-drained soil. Apply zineb, maneb, or copper several times, 7 to 10 
days apart, in cool, rainy weather. 

5. Verticillium Wilt — Plants turn yellow, wilt, and die. Often fail to bloom. Stems 
may turn brown. Control: See (15B) Verticillium Wilt under General Diseases. 



POTATO 339 



6. Curly-top, Aster Yellows — Plants severely stunted, bunchy, and yellowed. Control: 
Destroy infected plants when first found. Keep down weeds. Spray at least weekly 
with DDT and malathion to control leafhoppers which transmit the viruses. 

7. Spotted Wilt — Leaves stunted, twisted, and gradually turn yellow. Plants are 
stunted, pale, and bunchy. May die suddenly. Flower stems are stunted. Often 
twisted and bent over. Control: Same as for Curly-top and Aster Yellows (above) . 
The virus is transmitted by thrips. 

8. Black Ringspot — See under Cabbage. 

9. Leaf Smut — Pale leaf spots which turn dark brown or black, with a reddish border. 
Control: Same as for Bacterial Blight (above) . Spray or dust as for Downy Mildew 
(above) . 

10. Gray-mold Blight — See (5) Botrytis Blight under General Diseases. 

11. Leaf Nematode (poppy) —See (20) Leaf Nematode under General Diseases. 

12. Root-knot and other Nematodes (e.g., root-lesion) —See (37) Root-knot under 
General Diseases. 

13. Powdery Mildew — Pacific coast. Grayish-white, powdery mold patches on the leaves. 
Control: If serious enough, apply Kara thane or sulfur several times, at 10-day in- 
tervals. 

14. Black Mold— Sootlike mold patches on the foliage following attacks by insects. 
Control: Apply malathion as needed to keep insects in check. 

15. Rust (prickly-poppy) — See (8) Rust under General Diseases. Spray as for Downy 
Mildew (above) . 

POPPY - MALLOW - See Hollyhock 

POPULUS-See Poplar 

PORCELAIN BERRY -See Grape 

PORT ORFORD CEDAR - See Juniper 

PORTULACA — See Rose - moss 

POSSUMHAW - See Holly and Viburnum 

POTATO (Solanum) 

1. Common Scab — General. Shallow, rough, russeted, raised or pitted, corky areas 
on the tuber surface. Tubers often do not keep well in storage. See Figure 28A 
under General Diseases. Control: Plant scab-free tubers in scab-free soil. Treat 
seed-pieces as for Seed-piece Decay (below) . Three- or 4-year rotation. Include 
green manure crops (page 16) . Somewhat resistant varieties: Antigo, Avon, 
Blanca, Catoosa, Cayuga, Cherokee, Early Gem, Haig, Huron, Knik, Menominee, 
Navajo, Norland, Onaway, Ontario, Osage, Plymouth, Redkote, Redskin, Russet 
Burbank, Russet Rural, Russet Sebago, Sebago, Seneca, Tawa, and Yampa. Check 
to see if these varieties are adapted to your area by contacting a local grower, your 
extension horticulturist, or potato specialist. If practical, mixing sulfur, urea- 
formaldehyde (UF-85, Uracide, N-Dure) , or Terraclor into the top 6 inches of soil 
in the row may help. Check with the authorities mentioned above or your extension 
plant pathologist. Avoid application of alkaline materials, e.g., lime, wood ashes, 
and manure to potato soil. 

2. Early Blight, Target Spot — General. Small, dark brown, often zoned spots on the 
leaves. Spots may run together to kill a portion of the leaf. See Figure 156. Dark, 
slightly sunken spots develop on the stems and tubers in storage. Control: Apply 
maneb, zineb, or fixed copper at 7- to 10-day intervals, or just before rainy periods. 



340 



POTATO 




Fig. 156. Early blight of potato (extreme 

closeup). (Courtesy Illinois Agricultural 

Experiment Station) 



mMkk^Bt 



flf 




M 



Destroy (burn or dig under) volunteer potatoes and plant debris after harvest. 
Store tubers in a dry, well-ventilated location just above freezing. Keep down weeds. 
Dig tubers 2 to 3 weeks after the vines die. Plant disease-free, certified seed potatoes. 
Bordeaux mixture (6-3-50) is often suggested for the last 1 to 3 sprays when late 
blight threatens. Potato varieties differ in resistance. Three-year rotation with 
crops outside the potato-tomato family. 

Late Blight — General and serious in cool, damp weather. Large, irregular, dark 
green to grayish-purple, water-soaked areas on the leaves, petioles, and stems. In 
damp weather, a whitish mold growth appears — mostly on the underleaf surface. 
Infected areas later turn dark brown or blacken, dry out, and die. May resemble 
frost damage. Entire tops may die within a few days in cool, wet weather. Slightly 
sunken, dark brown to purple blotches form on the tubers. Tubers decay in stor- 
age. Control: Same as for Early Blight (above) . Maintain high, balanced fertility 
especially of phosphorus and potassium. Varieties resistant to one or more races of 
late blight: Ashworth, Avon, Boone, Catoosa, Cayuga, Cherokee, Delus, Empire, 
Fundy, Kennebec, Menominee, Merrimack, Ontario, Plymouth, Pungo, Russet 
Sebago, Saco, Saranac, Sebago, and Tawa. More highly resistant varieties will be 
available in the future. Check with your county agent, extension horticulturist, 
potato specialist, or plant pathologist. 

Tuber Rots — Cosmopolitan. Tubers rot slowly or rapidly in field or storage. Rot 
may be firm, watery, or slimy and foul-smelling (Bacterial Soft Rot) . Rots develop 
rapidly under warm, moist conditions. Mold may grow on affected areas. See Figure 
43A under General Diseases. Control: Store only sound, dry, blemish-free tubers 



POTATO 341 



in clean, well-ventilated storage at 40° F. First store tubers at 50° to 60° F. for 2 
to 3 weeks (or 60° to 85° F. for 1 week) to heal cuts and bruises. Check with your 
potato specialist or extension horticulturist. Also control measures as for Seed-piece 
Decays (below) . 

5. Seed-piece Decays — General. Seed-pieces rot in the soil. Poor stand. Emerging 
plants may be stunted and sickly with rolled yellowish leaves. Control: Plant cer- 
tified, disease-free tubers, well corked over, and treated with dichlone, chloranil, 
captan, maneb, zineb, thiram, or Semesan Bel. Follow the manufacturer's directions. 
The addition of streptomycin (200 parts per million) will often help control 
Blackleg. Avoid heavy, poorly drained soils. Four- to 6-year rotation. Before plant- 
ing, apply chlordane, aldrin, or dieldrin to the soil surface and then work it into 
the top 6 inches of soil. Follow the manufacturer's directions. This treatment con- 
trols wireworms and other insects which attack the seed-piece, roots, and tubers. 

6. Blackleg — General in wet seasons or in poorly drained soils. Yellowish, stunted, 
wilting plants. Stem base is slimy, black, and rotted. Infected plants are easily 
pulled up. Tubers show slimy, black, stem-end rot. Tuber rot develops rapidly in 
warm, moist storage. Often follows borers or other injuries. See Figure 43A under 
General Diseases. Control: Same as for Seed-piece Decays (above) . Control in- 
sects. See under Virus Complex (below) and Seed-piece Decays (above) . 

7. Virus Complex (mosaics, crinkle, calico, corky ringspot, leafrolls, mottle, streak, 
curly-top or green dwarf, aster yellows or purple-top, witches'-broom, vein-banding, 
ringspot, yellow spot, yellow dwarf) — General. May be serious. Symptoms vari- 
able depending on the viruses and strains involved, variety, age, weather condi- 
tions, and other factors. Leaves may show light green or yellow and dark green 
mottling, streaking, crinkling, or rolling of the leaves. Leaves may be stunted, stiff, 
leathery, and puckered. Plants often dwarfed and bushy. Aerial tubers often form 
along the stem. Corky areas may form in the tubers (Corky Ringspot) . Shoot tips 
may be purplish (Purple-top) . Yield is reduced. Control: Apply sprays at 7- to 10- 
day intervals to control insects, especially aphids and leafhoppers, which transmit 
the viruses. Use DDT and malathion. Alternate these materials with dieldrin. 
Keep down weeds. Plant only certified, virus-free seed tubers. Destroy the first in- 
fected plants when found. Varieties resistant to one or more viruses: Cherokee, 
Chippewa, Houma, Katahdin, Kennebec, Menominee, Merrimack, Mohawk, 
Ontario, Plymouth, Pungo, Redskin, Red Warba, Russet Sebago, Saco, Sebago, 
Tawa, and Warba. Check with your potato specialist or extension plant pathologist 
regarding the potato viruses prevalent in your area. 

8. Wilts — Potatoes are infected by all three common wilts: Fusarium, Verticillium, 
and Bacterial. See (15) Wilts under General Diseases. 

A. Fusarium Wilt, Dry Rot, Rusty Dieback — Most serious in hot, dry weather. 
Yellowish or bronzed leaves. Plants stunted, gradually or suddenly wilt and die. 
Brown streaks inside stems and tubers. Firm, leathery, cheesy, dry rot of tubers. 

B. Verticillium Wilt, "Pink Eye" — A cool season disease. Plants wilt gradually 
or suddenly around flowering time. Lower leaves become a mottled yellow and 
droop first. Leaflets may roll. Tips are yellowed. Stem-end of tuber is discolored 
around the eyes. Brown streaks occur inside the stems. Roots are decayed. 

C. Bacterial Wilt, Brown Rot — Mostly in southeastern states. See under 
Tomato. Plants gradually wilt and die. Stems turn brown, at first only on the 
inside. Brown rot of tubers with ooze sticking to the surface. 

Control for Wilts: Plant certified, disease-free seed grown in northern states. 
Treat seed as for Seed-piece Decays (above) . Four- to 6-year rotation excluding 
crops in the potato family. Avoid injuring tubers. Disinfect storage locations. See 



342 POTATO 

under Bacterial Ring Rot (below) . Increase ventilation in storage. Discard tubers 
with rot, discolored "eyes," or a sticky ooze on the surface. Varieties reported as 
having some resistance to Verticillium Wilt: Chippewa, Green Mountain, Houma, 
Katahdin, Menominee, Ontario, Pontiac, Red Beauty, Russet Burbank, Saranac, 
Sequoia, and Tawa. Sebago and Katahdin have weak resistance to Bacterial Wilt. 
Check with your extension horticulturist, potato specialist, or county agent regard- 
ing the adaptability of these varieties to your area. 
9. Rhizoctonia or Black Scurf, Stem Rot and Canker — General. Serious in cold, wet 
springs. Dark brown or black hard bodies (sclerotia) on the tuber surface which do 
not rub off. Dark brown, sunken cankers form at the base of the stem and on the 
stolons. Plants may be stunted with leaves rolled and a sickly yellow color. Green 
or reddish aerial tubers may form in the leaf axils near the stem base. Roots may 
be killed back. Stand and yield is often reduced. A light, grayish-brown powdery 
mold grows on the lower stem during damp summer weather. Control: Plant 
certified, disease-free seed in warm, well-drained, fertile soil. Treat seed as for 
Seed-piece Decays (above) . Terraclor worked into the top 4 to 6 inches of soil 
before planting may help on mineral soils. Follow the manufacturer's directions. 
Four- to 6-year rotation. Harvest early. Potato varieties show differences in sus- 
ceptibility. 

10. Hollow Heart — Large tubers develop irregular, hollow, center heart or cavity with 
a dark corky border. Common in seasons favorable for late, rapid growth (excessive 
soil moisture and fertility) . Control: Space plants closer together in the row. Plant 
varieties with a high dry-matter content. Check with your county agent, extension 
horticulturist, or potato specialist. 

11. Blackheart — Internal, dark gray to coal-black rot of tubers. Rotted tissue is firm. 
Control: Same as for Tuber Rots (above) . Do not store in large, solid piles. Dig 
promptly when the soil temperature is warm. 

12. Bacterial Ring Rot — General. Foliage symptoms are variable. Mottled rolled leaves 
on erect stems. Plants may wilt during the day and recover at night. Tubers often 
have yellowish pockets or a "cheesy" ring, about \/± inch deep under the skin, 
especially after a storage period. Rot develops rapidly in storage. Control: Plant 
certified, disease-free tubers. Disinfect cutting knives with mercuric chloride (1:500 
solution) or Semesan Bel (4 ounces per gallon) . Or plant small, uncut tubers. 
Stringent sanitation of all equipment, tools, and storage areas using formaldehyde 

(1 pint in 15 gallons of water) or copper sulfate (1 pound to 5 gallons) . Use new 
or clean sacks for seed tubers or dip in formaldehyde solution. Teton, Merrimack, 
and Saranac are resistant varieties. Control insects, especially Colorado potato 
beetles, plant bugs, aphids, and leafhoppers, which may transmit the causal bac- 
teria. See under Virus Complex (above) . 

13. Spindle Tuber — General. Symptoms differ greatly with the variety. Plants are 
often dwarfed, spindly, and more erect than normal with dwarfed, dark green 
leaves. Tubers usually elongated. Often pointed at the stem end and with shallow 
eyes. Control: Same as for Virus Complex (above) . 

14. Nematode Diseases— (1) Diseased plants may have small, round to irregular, 
knotty galls on the roots and tubers (Root-knot and Golden Nematode) . (2) Tuber 
may be spotted with small, raised pustules which tend to run together (Potato 
Rot and Stem Nematodes) . Infected areas later turn gray to brown, shrink, and 
become sunken. (3) Plants may be stunted and sickly with discolored, stubby or 
"bushy" roots (dagger, lance, reniform, ring, root-lesion, spiral, sting, stubby-root, 
and stunt or stylet nematodes) . Plants may become stunted and sickly. Often wilt 
during midday. Yield is often reduced. Control: Prevent contamination of clean 
soil. Plant certified, disease-free seed. Three- to 6-year rotation. Keep down weeds. 



POWDER-PUFF TREE 343 



Fumigate the soil if practical (pages 440-44) . Check with your extension plant 
pathologist or potato specialist. 
\5. Tipburn, Hopperbum — General. Tips and outer margins of leaves turn brown 
and curl in hot, dry weather. Plants turn pale green or yellow. Ripen prematurely. 
Yield is often reduced. Commonly confused with blights. Control: Control leaf- 
hoppers. See under Virus Complex (above) . Follow the best cultural practices. 
Check with your county agent, extension entomologist, or potato specialist. Potato 
varieties differ in resistance. 

16. Psyllid Yellows — Western half of the United States. Leaves turn yellow to purplish 
at the margins and roll upwards. Brown dead areas later develop in the leaves 
which wither and die prematurely. Plants are stunted and bushy. Aerial tubers 
sometimes form along the entire stem. Yield may be greatly reduced. Control: 
Spray with DDT to control psyllid insects. 

17. Black Dot Disease, Anthracnoses — General but a minor problem. Stems cankered 
and girdled just below the soil line by dark brown and dead areas with black dots. 
Foliage is yellowed with rolled leaves. Tops may die early. Tubers show silvery- 
gray patches, covered with black dots. Control: Plant certified, disease-free seed in 
well-drained soil. Four- to 6-year rotation. Burn or compost plant debris after 
harvest. 

18. Powdery Scab, Canker— Occasional in northern states. Small, dark, slightly raised 
pustules on the tubers which later break open and release powdery masses. Large, 
sunken cankers may form. Control: Same as for Black Dot Disease (above) . 

19. Knobbiness, "Second Growth," Malformed Tubers — Tubers branch and grow 
indeterminately. May develop cracks and cavities or the skin may be corky. Con- 
trol: Plant certified, disease-free seed of good size (\\/ 2 to 2 ounce seed-piece) . Main- 
tain as uniform a soil moisture supply as possible. Control diseases and insects. 
Spray regularly with a multipurpose mixture containing zineb or maneb plus 
either DDT or methoxychlor and malathion. 

20. Stem Rots, Stalk Disease, Southern Blight, Tuber Rots — See Bean White Mold. 

21. Minor Leaf Spots and Blotches — Spots of various colors and shapes on the leaves. 
Control: Same as for Early Blight (above) . 

22. Powdery Mildews — Usually minor. See (7) Powdery Mildew under General 
Diseases. Powdery white mold on both leaf surfaces. Leaves later turn yellow, 
wither, and die. Vines die back and later collapse. 

23. Leaf Scorch — Plants often stunted or dwarfed with tips and margins of the leaves 
scorched. May be curled. Control: Have the soil tested. Apply fertilizer as recom- 
mended. May be due to a deficiency of magnesium, potassium, or calcium. 

24. Web B light — Southeastern states. See under Bean. 

25. Crown Gall — See (30) Crown Gall under General Diseases. 

26. Root Rots — See (34) Root Rot under General Diseases. 

27. Black Walnut Injury — Plants growing under black walnut trees wilt and die. 
Roots are decayed. Control: Avoid growing within 50 feet or more of these nut 
trees. 

POTENTILLA-See Rose 

POTHOS-See Calla 

POT MARIGOLD, PRAIRIE - CONEFLOWER - See Chrysanthemum 

POWDER-PUFF TREE -See Calliandra 



344 PRAIRIEGENTIAN 

PRAIRIEGENTIAN - See Gentian 

PRAIRIE LILY -See Mentzelia 

PRAIRIE ROCKET -See Cabbage 

PRAYER PLANT -See Rabbit Tracks 

PRETTY - FACE - See Brodiaea 

PRICKLY - ASH - See Hoptree 

PRICKLY -POPPY -See Poppy 

PRIMROSE— See Evening - primrose and below 

PRIMROSE [CHINESE, ENGLISH, FAIRY], COWSLIP, OXLIP, POLYANTHUS 

(Primula); PIMPERNEL, SCARLET PIMPERNEL, ANAGALLIS (Anagallis); 

ROCKJASMINE (Androsace;,- SHOOTINGSTAR or AMERICAN COWSLIP, 

SIERRA SHOOTINGSTAR, MOSQUITO BILLS (DodecafheonJ; LOOSESTR/FE 

[GARDEN, SWAMP-, WATER or TUFTED], MONEYWORT or 

CREEPING CHARLIE (Lysimachia) 

1. Gray-mold Blight, Botrytis Blight, Flower Blight — Common indoors, occasional out- 
doors. Crowns and roots rot. Large rotted spots on the flower heads and leaves. 
Affected plant parts are covered with a dense gray mold in damp weather. Control: 
Avoid overwatering and overcrowding plants. Remove fading flowers. Indoors, 
keep water off the foliage and increase the air circulation. Plant in well-drained 
soil, sterilized if possible (pages 437-44) . Apply zineb or captan sprays before rainy 
periods. 

2. Fungus Leaf Spots or Blight, Anthracnose, Black Spot, Downy Mildew — Spots or 
blotches on the leaves. Of various colors, shapes, and sizes. Control: Same as for 
Gray-mold Blight (above) . In addition, apply zineb or fixed copper at 10-day in- 
tervals. Start when disease is first noticed. 

3. Bacterial Leaf Spot — Small, water-soaked spots with yellowish centers on the older 
leaves. Later the spots turn brown and develop pale yellowish halos. Spots may 
run together forming large, irregular, dead blotches. Control: Same as for Gray- 
mold Blight (above) . Plant resistant varieties. Spraying with fixed copper or strep- 
tomycin should be beneficial. 

4. Stem Rots, Root Rots — Leaves mottled and sickly. Later turn yellow and wither. 
Plants may wilt and collapse due to a brown or black rotting of the stem or roots. 
Control: Avoid overwatering. Where possible plant in clean or sterilized soil. See 
pages 437-44 in the Appendix. A soil drench of Terraclor (PCNB) applied when 
disease is first evident may be beneficial. 

5. Damping-off — Seedlings wilt, collapse, and die. Control: Same as for Gray-mold 
Blight (above) . 

6. Mosaics — Leaves mottled yellow and dark green, often cupped. Young leaves and 
plants are stunted. Flowers are flecked and streaked. Control: Destroy infected 
plants. Control insects, especially aphids, which transmit at least one virus. Use mal- 
athion or lindane. 

7. Spotted Wilt — Leaves and plants are stunted and yellowish. Few flowers are pro- 
duced. Irregular dead spots or blotches may develop in the leaves. Entire leaf may 
die. Control: Same as for Mosaics. Virus is spread by thrips. 

8. Aster Yellows — See (18) Aster Yellows under General Diseases. 



PRIVET 345 



9. Chlorosis — Primarily an indoor problem. Leaves develop a yellowish or whitish 
mottling. Varieties differ in susceptibility. Control: Avoid overwatering, overferti- 
lizing, and too acid or alkaline a soil. Follow the best cultural practices. Adding 
some iron sulfate to the soil or applying as a spray is often beneficial. 

10. Rusts — See (8) Rust under General Diseases. 

1 1. Powdery Mildew — See under Chrysanthemum. Foliage may wither and dry up. 

12. Root-knot — See (37) Root-knot under General Diseases. 

13. Leaf and Stem Nematode — See (20) Leaf Nematode under General Diseases. 

PRINCESFEATHER-See Cockscomb 

PRINCESSTREE - See Paulownia 

PRIVET [AMUR, BIGBERRY, CALIFORNIA, CHINESE, COMMON or 

EUROPEAN (many horticultural forms), GLOSSY or WAXLEAF, 
IBOLIUM, IBOTA, INDIAN, JAPANESE, LODENSE, QUIHOU, REGEL ] 

(Ligustrum) 

1. Anthracnose, Canker, Twig Blight, Dieback — General and serious. Leaves wilt, 
turn brown, shrivel, and cling to the stem. Twigs blighted and killed by girdling 
brown cankers at the base of the main stem. Common and Lodense privets are 
very susceptible. Control: Cut out and burn infected parts. Apply zineb or ferbam 
at weekly intervals during wet weather. Resistant varieties: Amur, California, Ibota, 
and Regel. 

2. Wood Rots, Collar Rot — Cosmopolitan. See under Birch, and (23) Wood Rot 
under General Diseases. 

3. Root Rots — Plants in hedge gradually die in one or several places. Areas tend to 
increase in size each year. Plants sickly and make poor growth. Foliage is thin and 
yellowish or brown. Roots are rotted. May be associated with root-feeding nema- 
todes (e.g., lance, needle, pin, ring, root-knot, root-lesion, spiral, stem, stubby-root, 
stylet or stunt) . Control: Dig up and destroy all of affected plants and 2 apparently 
healthy ones on each side. Include all the roots. Drench soil where these plants were 
growing using Vapam or V.P.M. Soil Fumigant, or replace with new soil. 

4. Crown Gall — Occasional. See under Apple, and (30) Crown Gall under General 
Diseases. 

5. Powdery Mildew — Powdery, whitish patches or blotches on the upper leaf surface. 
Control: If serious, dust or spray with sulfur or Karathane. 

6. Minor Leaf Spots, Leaf Blights — Prevalent during rainy seasons on overcrowded 
plants. Spots of various colors, sizes, and shapes on the leaves. Control: If serious 
enough, apply zineb, maneb, or fixed copper before rainy periods. Prune to thin 
out overcrowded plants. 

7. Sooty Mold — Blackish growth on leaves following insect attacks. Control: Apply 
malathion sprays to control insects. 

8. Root-knot — See under Peach, and (37) Root-knot under General Diseases. 

9. Stem Gall — More or less circular galls up to 2 inches in diameter at the crown or 
base of stem. Plants may die. Control: Cut out and burn stems infected with gall. 
Do not replant in the same area without first sterilizing the soil (pages 437-44) . See 
under Root Rots (above) . Avoid wounding stem bases. 

10. Chlorosis — Mineral deficiency in alkaline soils. See under Maple. Control: Have 
the soil tested. Treat as recommended. 



346 PROBOSCISFLOWER 

11. Mosaic, Variegation, Chlorotic Spot, Ringspot — Leaves mildly mottled, puckered, 
and distorted. May be stunted, spotted, or ringed with yellow. Control: Dig up and 
burn infected plants. Set out virus-free plants from a reputable nursery. 

12. Witches' -broom — See under Lilac. 

13. Leaf Nematode — See (20) Leaf Nematode under General Diseases. 

14. Thread Blight — See under Walnut. 

PROBOSCISFLOWER, DEVILSCLAW, UNICORNPLANT (Proboscidea) 

1. Fungus Leaf Spots — Brown to gray spots with reddish or purple margins. Control: 
Pick off and burn spotted leaves. If serious, spray several times during rainy 
weather, 10 days apart, using zineb, maneb, or fixed copper. 

2. Bacterial Leaf Spot — Minute, angular, sunken, water-soaked spots on the leaves, 
petioles, and stems. Spots may run together forming irregular, light brown patches. 
Plants may die. Fruit may become brown and shriveled. Control: Plant disease-free 
seed from healthy pods. Destroy infected plant parts and severely infected plants. 

3. Stem or Crown Rot — Stem rots at the soil line. Plants may wilt and collapse. Rotted 
area may be covered with a cottony mold. Control: See under Delphinium. 

4. Mosaics — See (16) Mosaic under General Diseases. 

5. Root Rot — See (34) Root Rot under General Diseases. 

PRUNE, PRUNUS-See Peach 

PRUNELLA -See Salvia 

PSEUDOLARIX - See Larch 

PSEUDOTSUGA-See Pine 

PSIDEUM-See Myrtle 

PTELEA-See Hoptree 

PTERIDIUM, PTERETIS, PTERIS - See Ferns 

PUCCOON - See Mertensia 

PUMPKIN -See Cucumber 

PUN1CA — See Pomegranate 

PURPLE - CONEFLOWER - See Chrysanthemum 

PURPLE - FLOWERED GROUNDCHERRY - See Tomato 

PURPLELEAF BUSH, PURPLELEAF PLUM - See Peach 

PURPLELEAF SPIDERWORT - See Rhoea 

PURPLE RAGWORT -See Chrysanthemum 

PURPLE ROCKCRESS - See Cabbage 

PURPLE SMOKEBUSH-See Sumac 

PUSCHKINIA-See Tulip 

PUSSYTOES — See Chrysanthemum 

PYCNANTHEMUM - See Salvia 



RASPBERRY 347 



PYRACANTHA - See Apple 

PYRETHRUM - See Chrysanthemum 

PYRUS-See Apple 

QUAKER BONNETS -See Pea 

QUAMOCLIT — See Morning - glory 

QUEEN - OF - THE - MEADOW, QUEEN - OF - THE - PRAIRIE - See Rose 

QUEENS - DELIGHT - See Castorbean 

QUERCUS-See Oak 

QUINCE -See Apple 

QUINCULA-See Tomato 

QUIVERLEAF-See Poplar 

RABBIT TRACKS, PRAYER PLANT, ARROWROOT (Maranta); CALATHEA 

1. Leaf Spots — See (1) Fungus Leaf Spot under General Diseases. 

2. Rust — See (8) Rust under General Diseases. 

3. Root-knot — See (37) Root-knot under General Diseases. 

4. Other Root Nematodes (burrowing, spiral) — Often associated with sickly plants. 
Control: Same as for Root-knot. Plant in sterilized soil. 

RADISH -See Cabbage 

RAINLILY-See Daffodil 

RANUNCULUS - See Delphinium 

RAPE — See Cabbage 

RASPBERRY [AMERICAN RED or COMMON RED, BLACK or BLACKCAP, 

GOLDEN EVERGREEN, PURPLE FLOWERING, PURPLECANE, RED, 

ROSELEAF, WESTERN RED, WHITE BARK, WHITE FLOWERING], 

BLACKBERRY [ ALLEGHANY or AMERICAN, CUT - LEAVED, 

EUROPEAN, EVERGREEN, HIGHBUSH, HIMALAYA, TRAILING, 

THORNLESS, YANKEE], BOYSENBERRY, DEWBERRY [CALIFORNIA, 

CULTIVATED AMERICAN, GRAPELEAF, NORTHERN, SOUTHERN], 

CLOUDBERRY, LOGANBERRY, MAMMOTH BLACKBERRY, 

SALMONBERRY, THIMBLEBERRY (Rubus) 

1 . Anthracnose , Spot Anthracnose, Gray Bark — General and serious. Small, reddish- 
brown to purple spots on young shoots and fruit spurs which enlarge, become 
more or less circular with sunken, light gray centers and purple borders. Fruits are 
often small, dry, and seedy. Small yellowish spots with a reddish-purple margin 
form on the leaves. Spots may later drop out leaving shot-holes. Heavily infected 
canes are stunted, gray-crusted, dry, crack, and often winter-kill. Black raspberries 
are very susceptible. See Figure 38A under General Diseases. Control: Remove and 
burn all fruiting canes right after harvest. Plant certified, disease-free plants. Re- 
move old cane "handles" when setting plants. Keep down weeds. Space plants. De- 
stroy badly infected canes when found. Destroy nearby wild brambles. Remove all 



348 



RASPBERRY 



weak canes in early spring. Apply lime-sulfur (4/ 5 pint in a gallon of water) as buds 
begin to swell in early spring. Then apply captan, ferbam, or maneb at about 
10-day intervals until berries start to ripen and again right after harvest. See the 
spray program in the Appendix (Table 10) . Resistant raspberry varieties: Blacks 
— Blackhawk, Dundee, Evans, Quillen; Purples — Marion, Potomac, Sodus; Reds — 
Cuthbert, Indian Summer, Latham, Newburgh, Ohta (Flaming Giant) , Ranere, 
and Turner. Check with your nurseryman or extension horticulturist regarding 
varieties adapted to your area. 

Spur Blight — General. Mainly on red raspberry. Chocolate-brown, dark blue or 
purplish-brown spots and encircling bands on the petioles and new canes. Af- 
fected areas are gray by fall. Canes are girdled. Laterals often wither and die early 
in the season. Spreading, brown, angular blotches occur on the leaves. Such leaves 
wither and drop early leaving the canes bare. Buds turn brown, shrivel, and die 
or produce yellowish leaves. See Figure 157. Control: Same as for Anthracnose 
(above) . Resistant raspberries: Chief, Columbian, Marcy, Ontario, and Viking. 
Check with your nurseryman or extension horticulturist regarding varieties adapted 
to your area. 
Cane Blights, Dieback — General. Fruiting canes usually wilt, wither, and die be- 




Fig. 157. Spur blight of red raspberry. 




Fig. 158. Raspberry cane blight. 
State University photo) 



(Iowa 



tween blossoming and fruit ripening. Gray, black-dotted, flattened cankers on the 
canes. Canes become cracked, brittle; easily break off. See Figure 158. Control: 
Same as for Anthracnose (above) . Fertilize and prune to keep plants vigorous. 
Prune at least 3 days before rain is predicted. Avoid wounding new canes. Con- 
trol insects using malathion and methoxychlor sprays. Columbian is a resistant 
purple raspberry. 

Crown and Root Gall, Cane Gall, Hairy Root — General and serious. Rough, warty, 
white to black overgrowths or galls on the roots, crown, and lower parts of the 
canes. Bark may split open and dry out. Plants often stunted, lack vigor, gradually 
die. Berries are seedy. See Figure 44C under General Diseases. Control: Plant certi- 
fied, disease-free plants in clean soil. Carefully dig up and burn all infected plants 
when first noticed. Avoid replanting in the same area for 3 or 4 years without first 
drenching the soil with Vapam or V.P.M. Soil Fumigant. Avoid injuring plants. 
Virus Decline (mosaics, mottle, leaf curls, rosette or streak, necrosis, dwarf) — Gen- 
eral and serious. Symptoms variable. Plants decline in vigor. Never recover. Leaves 



RASPBERRY 



349 




DISEASED 



HEALTHY 



Fig. 159. Raspberry leaf curl. 



Fig. 160. Orange rust of blackberry 




may be yellowish, light green to dark green, mottled, dwarfed, curled, wrinkled, 
and cupped downward. See Figure 159. Plants may be slightly to greatly stunted 
with dark green, bunchy, stiff, tightly curled leaves. Or foliage may be sparse with 
spindling canes. Fruit production gradually decreases over several years. Fruit 
often dry, seedy, and small. Canes may be brittle. Dark blue or bluish-violet spots 
or stripes may develop on the canes near the base (Streak) . Control: Plant certi- 
fied, disease-free plants. Dig up and burn infected plants when first found. De- 
stroy nearby (within 500 feet if possible) wild brambles before setting out new 
plants. Control aphids which transmit certain viruses, using malathion or nicotine 
sulfate. Resistant raspberries to one or more viruses: Indian Summer, Latham, 
Marcy, Milton, Newburgh, September, Taylor, Viking, and Washington. 

Fruit Rots — Cosmopolitan. Berries rot. Often soft and watery or may shrivel and 
become hard. Rotted areas may be covered with a gray, tan, or black mold. Con- 
trol: Handle fruit carefully to avoid bruising. Pick early in the day. Discard rotten, 
overripe, sunburned, or imperfect berries. Refrigerate promptly. Apply captan 
alone as berries start to color and just before harvest, especially if the period is wet. 

Orange Rusts— General. Underside of leaves is covered with bright, reddish-orange, 
dusty pustules in late spring. Leaves may wither and drop early. See Figure 160. 
New shoots are spindly or stunted with dwarfed or misshapen yellowish-green 
leaves. Infected plants never recover. Produce no fruit. Red raspberry and boysen- 
berries are highly resistant. Control: Plant only certified, disease-free plants. Care- 
fully dig up and burn infected plants when first seen, and before the pustules break 
open. Be sure to remove or kill the roots. Keep down weeds. Destroy nearby wild 
brambles. Spray as for Anthracnose (above) . Resistant blackberries: Boysen, Ebony 
King, Eldorado, Evergreen, Lawton, Lucretia, Russell, Snyder, and Young. 



350 RASPBERRY 

8. Yellow Rusts, Leaf and Cane Rusts — General. Small, lemon-yellow to orange, 
dusty pustules on both leaf surfaces, stems (canes) , and petioles. Pustules may be 
dark brown or black late in the season. Leaves are curled, later wither and drop 
early. Alternate host is white spruce or none. Control: Same as for Anthracnose 
(above) . Varieties differ greatly in resistance to these rusts. 

9. V erticillium Wilt, Blue Stem — New shoots are stunted, wilt, may turn bluish-black 
and die. Leaves are dull green then yellow to brown. Cup downward and fall early. 
Disease progresses upwards from the base. Fruits dry up before ripening. Broad, 
bluish-black streaks, extending from the base upwards, appear on older canes. 
Black raspberries are very susceptible. Plants gradually decline. See Figure 30D 
under General Diseases. Control: Plant certified, disease-free plants in well-drained 
soil where wilted eggplant, tomato, potato, strawberry, or raspberry plants have 
not occurred before. Dig up and destroy infected plants when found. Do not re- 
plant susceptible plants in the same soil for several years without first fumigating 
with Vapam, V.P.M. Soil Fumigant, or chloropicrin (pages 440-44) . Resistant 
blackberries: Burbank Thornless, Cory, Evergreen, Himalaya, Logan, Mammoth, 
and Thornless. Dewberry is rarely infected. 

10. Leaf Spots, Cane Spot — General. Small, round to irregular spots of various colors 
occur on the leaves and canes. Infected leaves may wither and drop early, usually 
starting at the base of the cane. Canes may be stunted and weakened. Yield is 
often reduced. Control: Same as for Anthracnose (above) . After harvest apply 
three or four sprays, 2 to 3 weeks apart, using captan, ferbam, zineb, fixed copper, 
or bordeaux mixture (4-4-50) . Carolina, Evergreen, Himalaya, and Lucretia black- 
berries have resistance to Septoria (Mycosphaerella, Sphaerulina) Leaf Spot, as 
do Dixie Mandarin and Van Fleet raspberries. 

W.Root Rots, Collar Rot — Plantings decline in vigor. Plants may die. Roots decay. 
Most serious in heavy, wet soils. See under Apple and Currant. May be associated 
with nematodes (e.g., dagger, lance, pin, ring, root-lesion, sheath, spiral, stem, 
stubby-root, stylet or stunt) . 

12. Powdery Mildews — Common but usually a minor problem. White powdery growth 
on the leaves, tips of new canes and even the fruit. Leaves are dwarfed, mottled, 
and distorted. Cane growth is stunted. Yield may be reduced. Most commercial 
varieties of red raspberry and dewberry are highly susceptible as is Blackhawk 
black raspberry. Control: Space plants and prune for good ventilation and sun- 
light. Keep down weeds. Cumberland and Logan raspberries have resistance. Most 
blackberries appear to be resistant. Apply a dormant or delayed dormant spray of 
lime-sulfur (see Table 10 in the Appendix) . Spray with Kara thane when mildew is 
first seen. 

IS. Winter Injury — Symptoms variable. Entire plants may die during the winter or 
up to harvest. Tips of canes die back or buds are killed. Berries may be irregular 
and aborted. The presence of other diseases frequently increases the severity of 
winter injury. Control: Practice recommended cultural practices for your area, e.g., 
mulching, fertilizing, and pruning. Provide for sturdy, mature wood in autumn. 
Prune out dead and injured canes. Control diseases and insects by following the 
spray program given in the Appendix (Table 10) . 

14. Sunscorch — Ripening fruit are gray and dull. Control: Follow recommended cul- 
tural practices. Same as for Anthracnose (above) . 

15. Male Berry (blackberry sterility) —New canes developing from affected plants are 
more vigorous. Eldorado and older varieties are quite susceptible. Control: Destroy 
affected plants, including all the roots. Do not start new plantings from "diseased" 
plants. Grow "immune" varieties of blackberries (e.g., Bailey, Ebony King, and 
Hedrick) . 

16. Sooty Blotches, Black Mildew — See (12) Sooty Mold under General Diseases. Con- 
trol: Apply malathion and methoxychlor to control insects. 



RHODODENDRON 351 

17. Downy Mildew — See (6) Downy Mildew under General Diseases. 

18. Fire Blight, Flower and Twig Blight (raspberry) —See (24) Fire Blight under 
General Diseases. 

19. Chlorosis — See under Maple and Walnut. Mostly in western states in alkaline 
soils. Due to a deficiency of one or more essential nutrients. 

20. Thread Blight — Southeastern states. See under Walnut. 

RATIBIDA — See Chrysanthemum 

REDBAY — See Avocado 

REDBUD, RED - CARDINAL - See Honeylocust 

REDCEDAR — See Juniper 

RED HAW -See Apple 

REDHOT - POKERPLANT or POKER - PLANT, TORCHLILY (Kniphofia, 

Tritoma) 

1. Root-knot — See (37) Root-knot under General Diseases. Control: Indoors grow 
plants in sterilized soil in sterilized containers. See "Soil Treatment Methods and 
Materials" in the Appendix. 

2. Leaf Spot — Small dark spots on the leaves. Control: Pick off and burn spotted 
leaves. Indoors keep water off the foliage. 

RED - ROBIN - See Cranesbill 

RED - VALERIAN - See Valerian 

REDWOOD -See Pine 

RESEDA— See Mignonette 

RETINOSPORA-See Juniper 

RHAMNUS-See Buckthorn 

RHEUM -See Rhubarb 

RHEXIA-See Deergrass 

RHODODENDRON [CAROLINA, CATAWBA, COAST, DAHURIAN, 

KOREAN, PIEDMONT, ROSEBAY or GREAT LAUREL], AZALEA 

[AMOENA, FLAME, GHENT, GLENN DALE, INDIAN, JAPANESE, 

KAEMPFERI, KAEMPFERI HYBRID, KURUME, KURUME HYBRID, 

MACRANTHA, MOLLIS or CHINESE, PINKSHELL, ROYAL, SNOW, 

SWAMP, SWEET or SMOOTH YELLOW], PINXTERBLOOM, DOWNY 

PINXTERBLOOM, RHODORA (Rhododendron) 

1. Leaf Spots, Leaf Scorch or Blotch, Anthracnose, Spot Anthracnose, Tar Spot, Blight 
— General. Small to large, round to angular or irregular, spots and blotches on the 
leaves. Often found on leaves damaged by frost, winter injury, sunscald, or insect 
injury. Spots may be silvery-white, yellow, gray, tan, red, reddish-brown, or dark 
brown in color. May be zonate with a conspicuous margin. Centers often sprinkled 
with black dots or possibly mold growth. Leaves may drop prematurely. See Figure 
161. Control: Grow only varieties adapted and recommended for your area. Vari- 
eties differ in resistance. Check with your local nurseryman, county agent, or exten- 
sion horticulturist. Grow plants in partial shade, sheltered from strong, dry, winter 
winds. Keep the soil well mulched with peatmoss, oak leaves, pine needles, or leaf- 
mold. The soil should be well-drained, acid (pH 4.5 to pH 5.5) , and high in or- 



352 RHODODENDRON 




Fig. 161. Rhododendron leaf spots. A. 
Cercospora, B. Phomopsis, C. Phyllosticta, 
D. Exobasidium. All 4 types of spots would 
never be found on the same leaf. 



ganic matter. Water during summer droughts. Be sure plants get the equivalent of 
an inch of rainfall every 10 days. Control insects with a mixture of DDT or lin- 
dane and malathion. Spray with captan, zineb, ziram, ferbam, or fixed copper at 
10-day intervals as leaves are expanding, and again just after flowering. Sprays 
may also be needed during the summer or fall where humid and moist. Add about 
1/2 teaspoonful of household detergent or commercial spreader-sticker to each gal- 
lon of spray. May combine with sprays to control insects. For additional information 
on "Growing Azaleas and Rhododendrons," get a copy of USDA Home and Gar- 
den Bulletin No. 71. 

2. Winter Injury, Leaf Burn — General where plants are grown near the limit of 
hardiness. Margins and tips of leaves turn brown in March or April. Control: Same 
cultural practices as for Leaf Spots (above) . 

3. Chlorosis, Yellow Leaf — General in neutral and alkaline soils, and next to brick or 
concrete foundations. New leaves are yellowed except for the main veins. See Figure 
79. If uncorrected, next year's flower buds may not form. Cold injury is often mis- 
taken for a nutrient deficiency. Control: Make the soil acid as given under Root and 
Stem Rots (below) . For immediate relief apply sprays containing ferrous (iron) 
sulfate (1 ounce per gallon of water) , ferbam (3 tablespoons per gallon) , or iron 
chelate following the manufacturer's directions. Repeat sprays as needed. 



RHODODENDRON 



353 



Root and Stem Rots, Wilt, Dieback, Twig Blights — Widespread. Leaves may be 
dull yellowish-green or water-soaked, then wilt and wither from a brown to black 
rot of the lower stem and roots. Or terminal buds and leaves turn brown, roll up, 
and droop. Brown, sunken, girdling cankers may form on the stem. Roots may 
decay. All parts above the canker or rot later wilt and die. Rhododendron varieties 
differ in susceptibility. May be associated with nematodes (e.g., dagger, lance, pin, 
ring, root-knot, root-lesion, sheath, sheathoid, spiral, stem, sting, stubby-root, stunt 
or stylet) . Control: Same as for Leaf Spots (above) . Avoid overwatering. Maintain 
an acid soil ranging between pH 4.5 and pH 5.5 by adding sulfur, acid fertilizer, 
aluminum sulfate, or acid peatmoss (page 16) . Check with your local nursery- 
man or extension horticulturist. Avoid wounding roots or stems and overwatering. 
Prune out and burn infected parts making cuts several inches below the brown 
canker. Remove and burn severely infected plants together with surrounding soil. 
Avoid planting close to lilacs. Sterilize the soil (pages 437-44) before planting. 
Flower Spot, Petal or Limp Blight (primarily azalea) —Serious in southern states, 
especially near the coast. Indian and Kurume azaleas are very susceptible. Small, 








Fig. 162. Azalea flower spot or limp blight. A. 

stage. 



Early stage of the disease, B. Later 



pale, round spots form on the underside of the flower petals. The spots are white 
on colored flowers and tan to brown on white flowers. When moist the spots en- 
large rapidly and run together forming large, irregular blotches. The flowers quickly 
go brown, limp, and mushy. See Figure 162. Rotted flowers are covered with a 
whitish mold. Control: Space plants. Grow where air circulation is good. Where 
practical, pick off and burn spotted flowers when first seen. Apply a light, misty 
spray 2 to 4 times weekly, during wet weather. Start a week before flowering and 
continue during the bloom period. Use zineb, thiram (Thylate) , Acti-dione, or 
maneb. Thylate (1 tablespoon per gallon) leaves less residue on the flowers than 
other materials. Special azalea kits are sold where this disease is prevalent. Apply 
Acti-dione RZ or Terraclor directly to the soil, under and around azalea plants, 
4 to 6 weeks before bloom is expected. Follow the manufacturer's directions. Then 
replace mulch with fresh material. Do not buy azaleas from the South unless plants 
have bare roots. Before planting, remove and burn any buds showing color. 



354 RHODORA 

6. Bud Blast and Twig B Ugh t — Widespread. Scales of terminal flower buds turn 
silvery-gray and are sprinkled with tiny black "bristles." Later the flower and leaf 
buds rot, shrivel, and turn light to dark brown in color. Such buds remain on the 
stem for 2 or 3 years; form rosettes. Twigs may die preventing flowering the next 
year. Control: Prune and burn infected buds and twigs when first seen. Remove 
and burn faded flower clusters. Destroy seedpods after blooming. Spray as for Leaf 
Spots and Flower Spot (above) . 

7. Leaf, Shoot and Flower Galls, "Rose Bloom," Witches' -broom — General. Leaves 
may be spotted with yellow or red, or turn light green or whitish and thickened, 
wholly or in part. The leaf surface may be deformed, blistered, (bladder-like) and 
curled. Whole flowers, individual petals, or seedpods may turn into thick, hard, 
waxy, irregular galls. The surface of affected parts becomes covered with a white 
to pink powdery bloom. Galls later turn brown and hard. Fleshy rosettes of leaves 
may be formed at the tip of a branch. Control: Hand pick and burn galls when 
first evident and before they turn white. Otherwise spray once before the leaves 
unfurl using bordeaux (3-1-50) , fixed copper, ferbam, or zineb (4 tablespoons per 
gallon) plus a spreader-sticker. Repeat 2 to 3 weeks later. Propagate from disease- 
free plants. Varieties differ in susceptibility. Spray after bloom as for Leaf Spots 
(above) . 

8. Witches' -broom — Distinct witches'-brooms are produced on coast rhododendron 
and rhododendron hybrids. Leaves turn yellowish-white and become covered with 
a dense, mealy growth on the undersurface. Control: Destroy infected plants since 
the fungus is systemic within the plant. 

9. Damping-off, Cutting Rots, Crown Canker — General. A serious nursery disease 
in cutting beds. Stems soften and rot at the soil line. Leaves may darken and drop 
early. Control: Increase air circulation and light. Avoid overcrowding and over- 
watering. Plant seeds in a sterile medium (e.g., sifted sphagnum moss) . Sterilize the 
soil (pages 437-44) or drench before planting using a mixture of Terraclor and 
phaltan or captan. Follow the manufacturer's directions. 

10. Powdery Mildews — White, powdery mold patches develop on the leaves in late 
summer. Control: Spray with sulfur or Karathane when mildew is first evident, 
Repeat as necessary. 

11. Rusts — Eastern states and Pacific Northwest where plants are growing near the 
alternate hosts, hemlock and spruce. Bright yellow to brownish, powdery pustules 
on the underside of the leaves. Control: Avoid planting near the alternate hosts. 
Spray as for Leaf Spots (above) using ferbam, maneb, or zineb. 

12. Crown Gall — Uncommon. Stem base of young plants is swollen. See (30) Crown 
Gall under General Diseases. 

13. Verticillium Wilt — Uncommon. See under Maple, and (15B) Verticillium Wilt 
under General Diseases. 

14. Thread B lights — Southeastern states. See under Walnut. 

15. Sooty Mold — See (12) Sooty Mold under General Diseases. Common on shrubs 
growing under tuliptree and other trees attacked by aphids, scales, mealybugs, 
whiteflies, and other insects. 

RHODORA — See Rhododendron 

RHODOTYPOS - See Jetbead 

RHOEA, PURPLELEAF SPIDERWORT, MOSES - IN - A - BOAT (Rhoea) 

1. Root Rot, Crown Rot — See under African-violet. 

2. Root-knot — See under African-violet. 



RHUBARB 355 



RHUBARB (Rheum) 



1. Root and Crown Rots, Southern Blight, Damping-off — Widespread. Leaves may 
turn yellow, wilt, and collapse from a rot of the stalk bases, crown and roots. 
Brownish-black streaks may occur in the lower ends of the stalks. Mold growth 
may cover affected tissues in damp weather. Often associated with nematodes (e.g., 
cyst, dagger, root-knot, spear, spiral, stem-rot, stylet or stunt) . Control: Plant 
healthy roots from disease-free fields or beds in well-drained, clean soil. Or soil 
fumigated with formaldehyde, Vapam, chloropicrin, etc. See "Soil Treatment 
Methods and Materials" in the Appendix. Spray the crowns early in the spring and 
again after harvest with fixed copper or bordeaux mixture. Dig up and destroy all 
infected plants together with 6 inches of surrounding soil. Five- to 6-year rotation. 
Avoid a wet mulch. 

2. Leaf and Stalk Spots and Blights, Anthracnose, Gray-mold Blight — Widespread. 
Round to irregular, variously colored spots on the leaves and stalks. Spots may 
enlarge and blight the leaf or fall out leaving ragged shot-holes. Leaves may wilt, 
wither, and die. Control: Collect and burn the tops in late fall. During harvest 
pick stems with spotted leaves first. If serious enough, apply captan, thiram, ferbam, 
maneb, phaltan, or fixed copper at 10-day intervals during damp periods. Avoid 
applications from 10 days before harvest until cutting is completed. Apply fertilizer 
in the spring and again after harvest. Varieties differ in resistance. Set out disease- 
free roots in an area where rhubarb has not grown for at least 3 years. Avoid over- 
crowding. 

3. Stalk Rots, Bacterial Soft Rots — Soft and brown or slimy, foul-smelling rot of the 
stalks in field or after harvest. Control: Same as for Leaf Spots (above) . Avoid 
wounding stalk bases. 

4. Ringspots, Mosaic — Pale yellowish to dead spots or rings on the leaves, usually 
with a pale green mottle. Young leaves show a well-defined to severe light and dark 
green mosaic mottle. Leaves are often crinkled and distorted. Symptoms may dis- 
appear in hot weather. Control: Dig up and destroy infected plants. Plant virus- 
free stock. Control aphids which transmit the viruses. Use lindane or malathion. 

5. Curly-top — Western states. See (19) Curly-top under General Diseases. No very 
characteristic symptoms are formed. Control: Same as for Ringspots (above) . The 
virus is spread by leafhoppers. 

6. Crown Gall — See (30) Crown Gall under General Diseases. 

7. Root-knot and Cyst Nematode — See (37) Root-knot under General Diseases. 

8. Verticillium Wilt — Plants gradually wilt, wither, and die. See (15B) Verticillium 
Wilt under General Diseases. 

9. Bacterial Wilt, Southern Wilt — See (15C) Bacterial Wilt under General Diseases. 

10. Rust — Uncommon. Large, carmine-red spots on the upper leaf surface and tiny, 
whitish, cluster cups on the underleaf surface. Alternate host: common reed grass 
(Phragmites) which grows in swamps and wet areas. Control: Same as for Leaf 
Spots (above) . 

11. Downy Mildew — Small to large, brown spots on the upper leaf surface. A whitish 
to violet-colored mold appears on the corresponding underleaf surface in cool, 
damp weather. Control: Plant healthy roots in soil which has not grown rhubarb 
for at least 3 years. Spraying may be needed in cool, wet weather. Apply zineb, fixed 
copper, or bordeaux mixture (4-4-50) at weekly intervals starting when the leaves 
begin to expand. 

12. Cracked Stem, Boron Deficiency — See under Celery. 



356 RHUS 

RHUS — See Sumac 

RIBES — See Currant 

RICINIS-See Castor -bean 

RIVINA-See Rougeplant 

ROBINIA-See Honeylocust 

ROCHEA — See Crassula 

ROCKCRESS, ROCKET -See Cabbage 

ROCKJASMINE - See Primrose 

ROCKSPIREA - See Holodiscus 

ROCKY MOUNTAIN GARLAND -See Fuchsia 

ROLLINIA — See Pawpaw 

ROMANZOFFIA - See Phacelia 

RORIPPA-See Cabbage 

ROSARYPEA - See Pea 

ROSE [BRIER, BRISTLY or GLOSSY - LEAVED, BURNETT, CAROLINA, 

CHINA or BENGAL, EVERGREEN, FAIRY, FLORIBUNDA or POLYANTHA, 

GRANDIFLORA, HYBRID PERPETUAL or REMONTANT, HUGO ROSE or 

GOLDEN ROSE OF CHINA, HYBRID TEA, JAPANESE, KOREAN, 

MINIATURE, MULTIFLORA, MUSK, PERPETUAL BRIER or RUGOSE, 

PRAIRIE, PRIMROSE, RAMBLER, SHRUB, SETIGERA 

HYBRIDS, SWEET BRIER or EGLANTINE, TEA, and WICHURIANA or 

MEMORIAL ] (Rosa;; GOATSBEARD (Ar uncus); COWAN I A; 

MOCK - STRAWBERRY (Ducfiesnea;,- MEADOWSWEET, QUEEN - OF -THE - 

MEADOW, QUEEN -OF -THE -PRAIRIE, DROPWORT (Filipendula); AVENS 

(Geum); OSOBERRY fOsmaromaj; CINQUEFOIL (Potentilla); BURNET 

[ AMERICAN, JAPANESE, SITKA ] (Sanguisorba) 

1. Rose Blackspot — General and serious on susceptible varieties. Roundish black spots 
with irregular or frayed margins on the leaves. Small black or purplish-red spots 
also occur on the young shoots and petioles. Infected leaves often turn yellow and 
fall early, weakening the plants. Defoliated plants are more susceptible to winter 
injury and drought. Blooming is reduced. See Figure 15C under General Diseases. 
Control: Buy best-quality, disease-free plants from a reputable nursery. Prune and 
burn old canes before growth starts in the spring. Indoors keep water off the foliage. 

-*^Rose varieties differ greatly in resistance. Check with your local nurseryman, rose 
grower, or extension horticulturist. Apply a dormant spray of lime-sulfur (1 part 
in 10 parts of water) before growth starts in the spring. Apply captan, phaltan, 
zineb, or maneb weekly throughout the season. Spraying is more effective than 
dusting. Cover the underside of leaves thoroughly. Collect and burn fallen leaves 
where practical. Space plants. Mulch plants throughout the growing season. Control 
insects and mites using a mixture of DDT or methoxychlor plus malathion. These 
materials can be mixed safely with the fungicides listed. 

2. Powdery Mildews — General and serious. Whitish-gray, powdery, mealy coating on 
the leaves, flower buds, and young stems. Causes stunting, reduced vigor, and 
blooming. Cane tips and flower buds may be distorted and killed. Leaves curl, 



ROSE 



357 



turn reddish or purplish, wither, and drop early. Most rose climbers, small-flowered 
ramblers, and some of the new floribundas are very susceptible. See Figure 21B 
under General Diseases. Control: Grow resistant rose varieties where possible. Check 
with a local nurseryman, a top rose grower, or your extension horticulturist. Space 
and prune plants properly. Apply the same dormant spray as for Blackspot (above) . 
Apply phaltan, sulfur, or Karathane with Blackspot sprays or dusts, or use Acti- 
dione alone following the manufacturer's directions. Do not apply sulfur, Kara- 
thane, or Acti-dione if the temperature is above 85° F. Avoid overfertilizing, 
especially with nitrogen. 

Rose Stem Cankers, Dieback, Cane Blight, Spot Anthracnose — General and serious. 
Stems die back from pruning cuts, graft unions, and flower stalk stubs due to light 
brown to black cankers. Cankers may start as small white, red, dark reddish, or 
purple spots. Several cankers develop cracks and are sprinkled with black dots, the 
fruiting bodies of the causal fungi. Cankers often girdle the stems causing the foli- 
age beyond to wilt and die. Entire plant may be killed. See Figure 38B under Gen- 
eral Diseases. Control: Plant only highest quality, disease-free plants from a repu- 
table nursery. "Cut-rate" plants are often infected. Prune out and burn cankered 
canes as soon as found. Make clean cuts 3 to 4 inches behind the canker but close 
to a bud. See Figure 7. Dip or swab pruning shears or knife in 70 per cent de- 
natured alcohol between cuts. Cover pruning or other wounds with tree wound 
dressing (page 25) . Spray as for Blackspot (above) . Keep plants in a healthy, 
actively-growing condition. Cut off old flowers. Do not fertilize plants late in the 
season. Indoors plant in sterilized soil. 

Rose Crown Gall, Stem Gall, and Hairy Root — General. Small to large rough galls 
or overgrowths on the roots, crown, and canes, usually near the soil line or graft 
union. Plants are often stunted and lack vigor. Flowering is reduced. See Figure 
44B under General Diseases. Hairy Root causes the production of a mass of small 
fibrous roots giving a witches'-broom effect which may arise from swellings. Con- 
trol: Dig up and burn infected plants. Plant disease-free nursery stock. Do not re- 
plant in the same area within 3 years without drenching the soil with Vapam or 
V.P.M. Soil Fumigant. Do not wound plants. Dip cutting wood in 0.5 per cent 
calcium hypochlorite (household bleach) for 15 to 20 minutes plus sanitary pre- 
cautions in handling cuttings. Disinfest benches, sacks, and tools, with commercial 
formaldehyde, 1 part in 50 of water. Practice strict sanitation. 

Rusts — General. Bright orange-colored, reddish, or orange-brown pustules on the 
petioles, young canes, underleaf surface, and buds. Pustules later turn dark brown 



Fig. 1 63. Rose rust. 




358 ROSE 

and finally black. Leaves may wilt, wither, and drop early reducing plant vigor. 
Most hybrid tea and climbing roses are susceptible. See Figure 163. Control: Same 
as for Blackspot (above) . Spray with maneb, zineb, ferbam, or sulfur. Plant resist- 
ant rose varieties. Prune out and burn infected canes which may be elongated and 
gall-like. 

6. Winter Injury (rose) — Canes die back from the tips. Plants may be entirely killed. 
Varieties differ greatly in susceptibility. Control: Plant hardy varieties recommended 
for your area. Protect for winter following recommended local practices. This may 
mean piling a cone of soil 8 inches to a foot deep around the base of plants plus 
adding a loose covering of pine twigs, clean straw, dry seaweed, or coarse sacking. 
If in doubt, check with your nurseryman, a successful rose grower, your county 
agent, or extension horticulturist. 

7. Fungus Leaf Spots, Spot Anthracnose — Widespread. Spots of various sizes, shapes, 
and colors on the leaves. Often with a distinct border. Spots may drop out leav- 
ing shot-holes. Leaves may be distorted and ragged. Plants may be defoliated and 
weakened. Control: Same as for Blackspot (above) . 

8. Bacterial Blight or Blast — Dark brown, sunken spots appear on the petioles and 
flower stalks. Flower buds die without opening. Follows cold, wet spring weather. 
Control: Prune and burn infected parts. 

9. Verticillium Wilt (rose) — Individual canes or entire plants gradually or sud- 
denly wilt near blooming time. Brownish to purplish streaks occur inside of canes 
at the base. Leaves on infected canes may turn yellow, wither, and drop early. 
Diseased plants may die gradually over a period of several years. Control: Dig up 
and burn infected plants. Use disease-free budwood or plants. Grow in clean, light, 
well-drained soil. Avoid wounding roots or crowns and replanting in the same area 
for 5 or 6 years without fumigating the soil first with chloropicrin, Vapam or V.P.M. 
Soil Fumigant, etc. See pages 440-44 in the Appendix. Manetti rootstock is highly 
resistant. 

10. Crown and Root Rots — Plants gradually decline in vigor and die. White fans of 
fungus growth are often found between the bark and wood. Control: Plant disease- 
free stock in sterilized soil. 

11. Rose Mosaics, Streak, Rosette, Infectious Chlorosis — Mostly on greenhouse roses. 
Symptoms differ greatly between varieties depending on the virus or virus strain 
involved. Many varieties shown no symptoms, especially outdoors. Ring, oakleaf, or 
watermark patterns may develop in some leaves. Irregular, yellow or brown to red- 
dish blotches and patterns may follow along the veins in the leaves. Leaves are 
often bent and distorted. Plants may be stunted and less vigorous. See Figure 164. 
Control: Do not use diseased plants for propagating. If practical, destroy infected 
plants. Replant with virus-free stock. 

12. Gray-mold Blight, Botrytis Blight, Blossom Blight, Storage Decay — Buds turn 
brown and are blasted. May fail to open. Brown spots develop on the flower petals. 
Sunken, grayish-black cankers may grow down the stems from infected buds or 
pruning cuts. Canes turn brown and soften in cold storage. In damp weather a 
grayish mold may grow on infected tissues. Control: Same as for Blackspot (above) . 
Carefully collect and burn infected buds, blossoms, and stems. Nurserymen com- 
monly dust stored roses with a fungicide, e.g., Terraclor or captan, or dip trimmed 
plants in captan solution (2 tablespoons per gallon) . Nurserymen pack roses in 
boxes lined with polyethylene-coated Kraft paper. 

13. Chlorosis — Leaves turn pale green or yellow to ivory-colored with the leaf veins 
remaining green until the last. See Figure 79. Common in alkaline soils. Control: 
Acidify the soil by adding sulfur, ammonium sulfate, or acid peatmoss (page 16) . 



ROSE 359 



Fig. 164. Rose mosaic. 




Work iron sulfate into the soil using 1 to 4 ounces per square foot or use iron 
chelate following the manufacturer's directions. Water the iron sulfate or iron 
chelate in well. 

14. Root-knot — Plants stunted. Produce inferior blooms. Plants sickly with small pale 
leaves. Small galls or knots are found on the roots. Somewhat similar root galls 
are produced by dagger nematodes (Xiphinema spp.) . Control: Plant disease-free 
roses in clean or sterilized soil (pages 437-44) . Keep plants vigorous by fertilizing 
and watering. Protect plants properly for winter. Rose rootstocks vary greatly in 
resistance. 

15. Root-lesion (Meadow) and other Nematodes (e.g., dagger, lance, pin, ring, sheath, 
spiral, stem, sting, stubby-root, stylet or stunt) — General. Plants stunted and may 
die back. Leaves yellowish. Root system is stunted with roots showing brown 
areas. May be associated with Hairy Root (above) . Control: Same as for Crown 
Gall and Root-knot (both above) . Set plants in fumigated soil. 

16. Rose Black Mold — Primarily a nursery disease. Serious on certain varieties (e.g., 
Manetti understock, Dr. Huey, and Rosa odorata) in grafting cases. Newly in- 
fected grafts (stock and scion) are first covered with a white or grayish mold which 
gradually turns into a black crust. Wood at grafts is discolored. Grafts do not take. 
Bud unions fail. Control: Use only disease-free stock for grafting, or soak 2 hours 
in a formaldehyde solution (1 part in 320 parts of water) . Use resistant or immune 
rootstocks where possible (e.g., Ragged Robin) . Plant in clean soil. Three-year 
rotation. Practice strict sanitation. 

17. Downy Mildew (rose, mock-strawberry, avens) —Primarily an indoor problem. 
Irregular, light to dark spots on the upper leaf surface with a whitish-gray, downy 
mold growing on the corresponding underside in damp weather. Leaves rapidly 
turn yellow, wither, and drop. Flowers may be slow or unmarketable. Control: 



360 ROSEBAY 

Same as for Blackspot (above) . Indoors, keep the humidity below 85 per cent and 
water off the foliage. Increase air circulation. 

18. Aster Yellows (avens) —See (18) Yellows under General Diseases. 

19. Leaf Smut (avens) —See (11) Smut under General Diseases. 

20. 2,4-D Injury — Leaves fernlike and twisted. See under Grape. Rose is very sus- 
ceptible. 

21. Thread Blight (rose) —Southeastern states. Plants may be defoliated. See under 
Walnut. Control: Spray as for Blackspot (above) . 

22. Crown Rot, Southern Blight — See (21) Crown Rot under General Diseases. 

23. Fire Blight (avens, cinquefoil, goatsbeard) — See under Apple. 

ROSEBAY — See Rhododendron 

ROSELLE, ROSE -OF -SHARON, ROSEMALLOW - See Hollyhock 

ROSEMARY -See Salvia 

ROSE-MOSS (Portulaca) 

1. Damping-off, Seed Rot — See under Beet, and (21) Crown Rot under General 
Diseases. 

2. Root-knot — See (37) Root-knot under General Diseases. 

3. White-rust — Branches and leaves are swollen and distorted with white pustules. 
Shoots may be spindly and erect. Control: Destroy infected plant parts. Keep down 
cruciferous weeds. See (9) White-rust under General Diseases. 

4. Curly-top — See (19) Curly-top under General Diseases. 

ROSE -OF -HEAVEN -See Carnation 

ROSE TREE OF CHINA -See Peach 

ROSINWEED — See Chrysanthemum 

ROSMARINUS -See Salvia 

ROUGEPLANT (Rivina) 

1. Leaf Spots — Spots of various sizes, shapes, and colors on the leaves. Control: Pick 
off and burn spotted leaves. If practical, spray at 10-day intervals during rainy 
periods using ferbam, zineb, or maneb. Indoors keep water off the foliage. Space 
plants. 

2. Rust — Small, orange-yellow spots on the foliage. Pustules later may become 
powdery and reddish-brown to a dark chocolate-brown in color. If severe, leaves 
may wither and die early. Control: Same as for Leaf Spots (above) . 

3. Root Rots — See under Geranium, and (34) Root Rot under General Diseases. 
May be associated with nematodes (e.g., burrowing) . 

ROWAN TREE -See Apple 

ROYSTONEA-See Palms 

RUBBER PLANT -See Fig 

RUBUS — See Raspberry 

RUBY GLOW -See Spirea 



ST.-JOHNS-FIRE 361 



RUDBECKIA — See Chrysanthemum 

RUE -ANEMONE -See Anemone 

RUELLIA-See Clockvine 

RUSSIAN - OLIVE, SILVERBERRY, ELAEAGNUS [AUTUMN, CHERRY, 
THORNY ] (Elaeagnus) BUFFALOBERRY [ RUSSET, SILVER ] (Shepherdia) 

1. Leaf Spots — Spots of various colors, sizes, and shapes on the leaves. Control: If 
serious enough, apply zineb or captan at 10- to 14-day intervals during wet, spring 
weather. 

2. Trunk Canker — Oval to elongated, sunken cankers which girdle stems and may 
kill trees. Affected wood under the bark turns brown or black. A gummy brown sap 
may appear at the margins of some cankers. Control: Keep trees free of wounds 
and growing vigorously. Carefully cut out cankers and all discolored wood. Dis- 
infect wound with household bleach and paint with a tree wound dressing (page 
25) . 

3. Twig and Branch Cankers, Diebacks — See under Maple. 

4. Rusts — Yellowish spots on the leaves. Alternate hosts: Carex, Calamagrostis, or 
none. Control: Same as for Leaf Spots (above) . 

5. Crown Gall, Hairy Root — See under Apple, and (30) Crown Gall under General 
Diseases. 

6. Powdery Mildews (buffaloberry, silverberry) — Powdery, white mold patches on 
the leaves. Control: If serious enough, apply Karathane or sulfur twice 10 days 
apart. 

7 '. V ' erticillium Wilt — Leaves on certain branches turn yellow, wither, and drop 
early. A brown discoloration occurs in the wood just under the bark. Control: 
See under Maple. 

8. Thread Blights — Southeastern states. See under Walnut. 

9. Seedling Blights, Damping-off — See under Pine. 

10. Root Rot — See under Apple, and (34) Root Rot under General Diseases. 

11. Wood Rot — See under Birch, and (23) Wood Rot under General Diseases. 

12. Mistletoe (elaeagnus) —See (39) Mistletoe under General Diseases. 

RUSTYLEAF - See Blueberry 

RUTABAGA -See Cabbage 

RYEGRASS — See Lawngrass 

SABAL-See Palms 

SAFFLOWER — See Chrysanthemum 

SAGE — See Salvia 

SAGUARO-See Cacti 

ST. - ANDREWS - CROSS - See St. - Johns - wort 

ST. AUGUSTINE GRASS-See Lawngrass 

ST. -JOHNS -FIRE -See Salvia 



362 ST.-JOHNS-WORT 

ST. - JOHNS - WORT [BUCKLEY, BUSHY f KALMS, MARSH, SHRUBBY], 

AARONSBEARD, GOLDFLOWER, SUNSHINE SHRUB (Hypericum); 

ST. - PETERS - WORT, ST. - ANDREWS - CROSS (Ascyrum) 

1. Leaf and Stem Spots — Spots of various colors, shapes, and sizes on the leaves. Some- 
times on stems and flower bracts. Causes little injury, but may be a nuisance. Con- 
trol: Apply zineb or maneb during wet periods. Collect and burn fallen leaves. 

2. Rusts — General over much of the United States. Pustules vary from yellow to 
orange in the spring to reddish-brown and finally black, dusty pustules on the 
leaves late in the season. Control: If serious enough, same as for Leaf Spots 
(above) . 

3. Powdery Mildew (hypericum) — See (7) Powdery Mildew under General Diseases. 

4. Root-knot — See (37) Root-knot under General Diseases. 

SAINTPAULIA-See African - violet 

ST. - PETERS - WORT - See St. - Johns - wort 

SALAL-See Heath 

SALIX-See Willow 

SALMONBERRY- See Raspberry 

SALPIGLOSSIS - See Tomato 

SALSIFY -See Lettuce 

SALVIA, SAGE [BLUE, GARDE, SCARLET], ST. -JOHNS - FIRE (Salvia); 

BASILWEED (Clinopodium); COLEUS; DITTANY, STONEMINT (Cunila); 

DRAGONHEAD fDracocepfia/um; ; HYSSOP (Hyssopus); 

LAVENDER (Lavandula); LIONS - EAR or LIONS - TAIL (Leonof/s); 

SWEET MARJORAM (Marjorana); HOREHOUND (Marrubium); 

BALM (Melissa); MINT, CREEPING MINT, PEPPERMINT, SPEARMINT 

(Mentha) YERBA-BUENA (Micromeria); BELLS OF IRELAND (Molucella); 

BEEBALM, HORSEMINT, LEMON MINT, OSWEGO -TEA, WILDBERGAMOT 

(Monarda); MONARDELLA; NEPETA, CATNIP, GROUND - IVY (Nepeta); 

BASIL [AMERICAN, SWEET] (Ocimum); FALSE - DRAGONHEAD 

(Physostegia); SELFHEAL, HEAL-ALL (Prunella); MOUNTAIN -MINT 

(Pycnanthemum); ROSEMARY (Rosmarinus); SKULLCAP (Scutellaria); 

BETONY, HEDGENETTLE, LAMBS -EARS, WOUNDWORT (Stachys); 

GERMANDER [ AMERICAN, SHRUBBY ] (Teucrium); THYME, 

MOTHER -OF -THYME or CREEPING THYME (Thymus) 

1. Leaf Spots, Anthracnose , Spot Anthracnose, Tar Spot — Spots of various sizes, 
shapes, and colors on the leaves. Often with a distinct margin. Some leaves may 
wither and drop early. Spots may also occur on the stem and rootstocks. Control: 
Pick off and burn infected leaves. If practical, spray during wet periods using zineb, 
maneb, or captan. Burn tops in the fall. 

2. Root-knot — Plants may be stunted and sickly with gall-like nodules on the roots. 
Coleus is highly susceptible. See (37) Root-knot under General Diseases. 

3. Rusts (basilweed, dittany, germander, leonotis, mint, monarda, monardella, moun- 
tain-mint, physostegia, sage, salvia, stachys, yerba-buena) — Yellow-orange, reddish- 
brown, dark brown or black, dusty pustules on the leaves, stems, and petioles. 



SANGUISORBA 363 



Leaves may wither and die early. Young mint shoots are swollen, distorted, and 
twisted in the spring. Control: Same as for Leaf Spots (above) . Use zineb, maneb, 
or sulfur. Check with your county agent or extension plant pathologist. Mint roots 
(rhizomes) for forcing can be soaked in hot water (112°F.) for 10 minutes to 
destroy the rust fungus. 

4. Crown Rots, Stem Rots, Southern Blight, Damping-off, Cutting Rots — Seedlings 
or older plants wilt and collapse from a rot at the soil line. Stem base may be 
covered with a cottony or gray mold. Cuttings are discolored and rot at the base. 
Control: Start seeds and cuttings in sterilized soil. See pages 437-44 in the Appendix. 
Avoid overwatering and overcrowding. Plant in well-drained soil. Dig up and 
burn infected plants and several inches of surrounding soil. Treat soil as for Del- 
phinium, Stem Canker (page 208) . 

5. Root and Rhizome Rots — See under Geranium, and (34) Root Rot under General 
Diseases. May be associated with nematodes (e.g., lance, needle, ring, root-lesion, 
sheath, spiral, stubby-root, stylet or stunt) . 

6. Mosaic (primarily coleus and nepeta) — Symptoms differ with the variety. Leaves 
are mottled light and dark green, puckered, and crinkled. May show small dead 
spots, ringspots, oakleaf, or other irregular markings. Leaves or entire plants may 
be stunted and distorted. Control: Destroy infected plants. Use disease-free stock 
or select cuttings from healthy plants. 

7. Verticillium Wilt (coleus, mint, monarda) — Plants stunted and may be killed. 
Leaves drop prematurely. See (15B) Verticillium Wilt under General Diseases. 
Some peppermint hybrids are resistant. 

8. Blossom Blight, Gray-mold Blight, Leaf Blight — Soft brown spots on the flowers, 
stems, and leaves. Stems may rot and flower clusters often collapse. A gray mold may 
grow on affected parts in cool, moist weather. Control: Cut off and burn infected 
plant parts. Spray several times during cool, moist weather using captan or zineb. 

9. Downy Mildew (dragonhead, false-dragonhead, salvia) — See (6) Downy MildeAv 
under General Diseases. 

10. Leaf Nematode (coleus, salvia) —Brown or blackish blotches on the leaves, 
bordered by the larger veins. Heavily infested leaves may die from the base up- 
wards. Control: See under Chrysanthemum. 

11. Powdery Mildews (betony, mint, prunella, salvia, skullcap, stachys) —See (7) 
Powdery Mildew under General Diseases. 

12. Bacterial Leaf Spot (catnip) —See (2) Bacterial Leaf Spot under General Dis- 
eases. 

13. Fusarium Wilt (catnip) —See (15A) Fusarium Wilt under General Diseases. 

SAMBUCUS-See Snowberry 

SANCHEZIA - See Clockvine 

SANDMYRTLE - See Labrador - tea 

SAND -VERBENA -See Four -o'clock 

SANDWORT — See Carnation 

SANGUINARIA-See Poppy 

SANGUISORBA - See Rose 



364 SANSEVIERIA 

SANSEVIERIA, BOWSTRING HEMP (Sansevieria) 

1. Bacterial Soft Rots — Soft, mushy, foul-smelling rot of the leaves at the soil line. 
Plants collapse. Control: Avoid overwatering and overcrowding. Plant in sterilized 
soil (pages 437-44) . Do not propagate from diseased plants. 

2. Leaf Spots — More or less circular spots on the leaves. Often with a distinctive 
border. Spots may dry up and drop out. Leaves are sometimes girdled and killed 
by the fusing together of several spots. Control: Cut out and destroy infected 
leaves. Indoors, keep water off the foliage and the humidity as low as practical. 
If needed, spray when the spots are first seen, using zineb, captan, maneb, or fixed 
copper plus wetting agent. 

3. Root-knot and Root-lesion Nematodes — Associated with sickly plants. See (37) 
Root-knot under General Diseases. Control: Soak bare-root plants in hot water 
(122° F.) for 10 minutes. Cool, then plant in clean or pasteurized soil. 

SAPINDUS-See Soapberry 

SAPIUM — See Castorbean 

SARSAPAR1LLA — See Acanfhopctnax 

SASSAFRAS — See Avocado 

SATIN - FLOWER - See Fuchsia 

SAWARA - CYPRESS - See Juniper 

SAXIFRAGE (Saxifraga) - See Hydrangea 

SCABIOSA, PINCUSHION FLOWER, SWEET SCABIOUS (Scabiosa) 

1. Powdery Mildew — Powdery, white coating on the leaves. Control: Space plants. 
Dust or spray several times, 10 days apart, using sulfur or Karathane. 

2. Stem Rot, Crown Rot, Southern Blight — See (21) Crown Rot under General 
Diseases. 

3. Curly-top — Western states. See (19) Curly-top under General Diseases. 

4. Aster Yellows — See (18) Yellows under General Diseases. 

5. Root Rot — See under Geranium, and (34) Root Rot under General Diseases. 

6. Black Ringspot — See under Cabbage. 

SCARBOROUGH -LILY -See Daffodil 

SCARLET EGGPLANT -See Tomato 

SCARLET PIMPERNEL -See Primrose 

SCARLET RUNNER BEAN - See Bean 

SCHEFFLERA 

1. Leaf Spots — Small to large, round to irregular, brown spots and blotches on the 
leaves. Infected leaves may wither and drop early. Control: Indoors keep water off 
the foliage. Outside try spraying during wet periods with zineb, maneb, or captan 
to which a wetting agent has been added. 

2. Root-knot — See (37) Root-knot under General Diseases. 



SECHIUM 365 



SCHINUS-See Sumac 

SCHIZANTHUS - See Tomato 

SCIADOPITYS - See Pine 

SCILLA-See Tulip 

SCINDAPSUS - See Calla 

SCORPIONWEED - See Phacelia 

SCORZONERA - See Lettuce 

SCOTCH BROOM -See Broom 

SCREWPINE (Pandanus) 

1. Leaf Spots — Small to large spots develop on the leaves, working inward from the 
margin. Control: Prune off infected leaves and spray with fixed copper, zineb, or 
both. Indoors keep water off the foliage. Destroy badly infected plants. 

2. Burrowing Nematode — Associated with sickly, declining plants. Control: See Root- 
knot under Peach. 

SCURVY WEED, SEAKALE - See Cabbage 

SCUTELLARIA - See Salvia 

SEA HOLLY -See Celery 

SEAKALE -See Cabbage 

SEA -LAVENDER, STATICE (Limonium); SEA -PINK, THRIFT (Armeria) 

1. Leaf Spots — Spots of various sizes, shapes, and colors on the leaves. Heavily spotted 
leaves drop early. Control: Pick off and burn affected parts. If serious enough, 
apply zineb or maneb at 10- to 14-day intervals, starting when the first spots are 
evident. 

2. Gray-mold Blight, Botrytis Flower Blight — Brown rotting spots on the shoots and 
flowers. A gray mold may cover affected parts in damp weather. Control: Same as 
for Leaf Spots (above) . 

3. Rusts — Not very common. Yellow, yellow-orange, reddish-brown, or black powdery 
pustules on the leaves. Control: Destroy affected plants. Spray the remainder as 
for Leaf Spots (above) . 

4. Aster Yellows — See (18) Yellows under General Diseases. 

5. Root Rot — See under Geranium, and (34) Root Rot under General Diseases. 

6. Crown Rots (statice) — Stem rots at or near the soil line. Plants are easily pulled 
up. Water-soaked spots, which later darken, occur on the leaves and petioles where 
they touch the soil. Control: Suggest soil treatment as for Cabbage Wirestem. 

7. Root-knot, Cyst Nematode — See (37) Root-knot under General Diseases. 

8. Spotted Wilt, Ringspot — See (17) Spotted Wilt under General Diseases. Control: 
Destroy infected plants. 

SEA - PINK — See Sea - lavender 

SECHIUM -See Cucumber 



366 SEDUM 

SEDUM, LIVEFOREVER, STONECROP, WALL PEPPER, WORMGRASS (Sedum); 

CRASSULA, JADE PLANT (Crassula); ECHEVERIA; KALANCHOE or 

BRYOPHYLLUM; ROCHEA; HOUSELEEK, HEN -AND - CHICKENS 

(Sempervivum) 

[.Stem and Leaf Rot, Crown Rots, Southern Blight, Root Rot, Wilt — Brown to 
black, water-soaked areas on the stem, often at the soil line. May extend upwards 
into the flower stalks and down into the roots. Affected areas may be covered with 
a dense cottony mold. Tops of plants soon wilt. Plants may die out in patches in 
warm, humid weather. Roots decay. Control: Set disease-free plants in clean, well- 
drained soil. Avoid overwatering, too deep planting, overfertilizing, and packing 
the soil too closely around the crowns. Destroy infected plants or plant parts and 
drench the remainder with zineb (2 tablespoons per gallon) . Do not replant in 
the same area without first sterilizing the soil with heat or chemicals. See pages 
437-44 in the Appendix. Spray at weekly intervals during cool, wet weather using 
zineb or captan. 

2. Rusts (echeveria, hen-and-chickens, houseleek, liveforever, stonecrop) — Dark, 
powdery pustules on the leaves. The center leaves of houseleek are unusually long, 
narrow, erect, and a pale yellow color. Small, dark, reddish-brown pustules break 
out on both leaf surfaces. Affected plants do not bloom. Control: Pull up and burn 
infected houseleek plants for they will not recover. Apply zineb, maneb, sulfur, 
or dichlone two to three times 10 days apart on neighboring plants or other hosts. 

3. Root-knot — See (37) Root-knot under General Diseases. 

4. Leaf Spots, Blotch, Anthracnose (crassula, liveforever, stonecrop) — Round, dark 
spots or blotches on the leaves. Leaves may drop quickly. Control: Collect and burn 
fallen leaves. Try spraying as for Rusts when spots first appear. Repeat before rainy 
periods. 

5. Powdery Mildew (kalanchoe) — Grayish-white, powdery growth on the leaves. 
Leaves may wither and drop early. Control: Indoors, keep the humidity down and 
increase both light and air circulation. Avoid overfertilizing. Apply sulfur or Kara- 
thane twice, 10 days apart. 

6. Crown Gall (kalanchoe) — See (30) Crown Gall under General Diseases. 

7. Fusarium Wilt (sedum) — California. Leaves turn yellow and drop off, starting at 
the base of the stem. Plant may wither and die. Control: Same as for Stem and Leaf 
Rot (above) . 

8. Leaf Nematode (crassula) — See (20) Leaf Nematode under General Diseases. 

SELF - HEAL - See Salvia 

SEMPERVIVUM - See Sedum 

SENECIO — See Chrysanthemum 

SENNA — See Honeylocust 

SENSITIVE PLANT -See Pea 

SEQUOIA -See Pine 

SERVICEBERRY, SERVICETREE, SHADBLOW, SHADBUSH-See Apple 

SHALLON-See Heath 

SHALLOT -See Onion 



SILVER LACEVINE 367 



SHAMROCK -See Oxalis 

SHASTA DAISY -See Chrysanthemum 

SHEEP -LAUREL -See Blueberry 

SHELL FLOWER -See Gladiolus 

SHEPHERDIA-See Russian -olive 

SHORTIA-See Galax 

SHRUB - ALTHAEA - See Hollyhock 

SHRUB - YELLOWROOT - See Clematis 

SICANA — See Cucumber 

SIDA, SIDALCEA-See Hollyhock 

SILENE — See Carnation 

SILKGRASS - See Yucca 

SILK -OAK (Grevillea) 

1. Root-knot — See (37) Root-knot, under General Diseases. Control: Sterilize potting 
soil and container before planting. See pages 437-44 in the Appendix. 

2. Dieback, Gum Disease — See (22) Stem Blight under General Diseases. Control: 
Prune out and burn dead or dying parts. Indoors keep water off the foliage. 

3. Root Rot — See (34) Root Rot under General Diseases. Control: Same as for Root- 
knot. Avoid overwatering and overfertilizing. 

SILKTASSEL - BUSH - See Dogwood 

SILKTREE - See Honeylocust 

SILPHIUM — See Chrysanthemum 

SILVERBELL [CAROLINA, MOUNTAIN], SNOWDROP-TREE (Halesia); 
SNOWBELL [ FRAGRANT, JAPANESE ] (Styrax) 

1. Leaf Spot — Large, irregular, rusty-brown blotches on the leaves. Control: See 
under Maple. 

2. Wood Rot — See under Birch, and (23) Wood Rot under General Diseases. 

3. Root-knot — See under Peach, and (37) Root-knot under General Diseases. 

SILVERBERRY - See Russian - olive 

SILVER KING -See Chrysanthemum 

SILVER LACEVINE, DWARF LACE PLANT (Polygonum) 

1. Leaf Spots, Tar Spot — More or less round, gray or black spots on the leaves. Leaves 
may wither and drop early. Control: Pick off and burn infected plant parts. If prac- 
tical, spray during wet summer weather using zineb or maneb. 

2. Smuts — Roundish pustules on the leaves and fruit which break open and release 
black powdery masses. Control: Pick off and burn infected parts before the pustules 
break open. Destroy plants which show smut each year. 

3. Rusts — General. Small, brown, powdery pustules on the underside of leaves and 
stems. Pustules later turn black. Alternate hosts include Geranium. Control: If 



368 SILVER THREADS 

serious enough, apply ferbam, zineb, or maneb several times, starting 2 weeks 
before rust normally appears. 

SILVER THREADS (Fittonia) 

1. Stem and Root Rot — Stems and roots decay. Plants are stunted and sickly. Often 
wilt and collapse. Control: Start plants in sterilized soil (pages 437-44) . Infected 
plants may sometimes be cured by immersing them in hot water (120° to 124° F.) 
for 30 minutes. Use the lower temperature for unhardened plants. After treating, 
divide the plants or take cuttings and root or plant in a steamed mixture of perlite 
and peat. Keep water off the foliage. 

2. Leaf Spot — See (1) Fungus Leaf Spot under General Diseases. 

3. Root-knot — See (37) Root-knot under General Diseases. 

SINNINGIA — See African - violet 

SISYRINCHIUM-See Iris 

SKULLCAP -See Salvia 

SKYROCKET -See Phlox 

SLIPPERWORT - See Snapdragon 

SMELOWSKIA - See Cabbage 

"SMILAX" of FLORISTS - See Asparagus 

SMOKETREE - See Sumac 

SNAPDRAGON (Antirrhinum); SLIPPERWORT (Calceolaria); 

PAINTED -CUP, INDIAN PAINTBRUSH 

(Castilleja); TURTLEHEAD (Chelone); COLLINSIA, BLUELIPS, 

BLUE - EYED - MARY, CHINESE HOUSES (Collinsia); FOXGLOVE 

[COMMON, YELLOW] (Digitalis); LINARIA, TOADFLAX, 

BUTTER -AND -EGGS, KENILWORTH IVY (Linaria); MAURANDYA; 

MONKEYFLOWER (Mimulus); PENSTEMON, BEARD - TONGUE, 

LAVENDER QUEEN (Penstemon); SYNTHYRIS; TORENIA, 

WISHBONE FLOWER (Torenia); MULLEIN (Verbascum) 

1. Rusts (snapdragon, collinsia, Indian paintbrush, monkeyflower, painted-cup. 
penstemon, synthyris, toadflax, turtlehead) — General and serious on snapdragon. 
Small, reddish-brown or chocolate-brown, powdery pustules on the leaves (mostlv 
underleaf surface) , stems, and seedpods. Penstemon pustules are yellow. Infected 
parts may wilt, shrivel, and die. Small weak flowers are produced. See Figure 22A 
under General Diseases. Alternate hosts: Wild grasses, nines, none, or unknown. 
Control: Space plants. Keep down weeds. Collect and burn the tops in the fall. 
Plant disease-free seed, cuttings, or transplants. Resistant varieties of snapdragons 
are available, e.g., Alaska, Apple Blossom, Artistic, Campfire, Canary Bird, Copper 
King, Crimson, Loveliness, Red Cross, Rosalie, Snow Giant, and Yellow Giant. 
Indoors avoid sprinkling the foliage when watering. Keep the humidity as low as 
practical. Control insects with malathion sprays. Apply zineb, ferbam, chloranil, 
dichlone, or maneb at 7- to 10-day intervals. Start when plants are set in the 
garden. 

2. Gray-mold Blight, Botrytis Blight — Cosmopolitan in damp areas. Soft brown rot 
of the leaves, stems, flowers, cuttings, and seedlings. Flower spike may wilt sud- 



SNAPDRAGON 369 



denly, collapse, and die. A grayish-brown mold may grow on affected areas. Control: 
Collect and burn the tops in the fall. Space plants. Keep down weeds. Cut flower 
spikes as early as possible. Indoors, control heat, increase ventilation, and keep 
down the humidity. Apply captan or zineb twice weekly in wet weather. Mix 
Terraclor 75 per cent (12 ounces per 100 square feet) into the top 4 to 6 inches of 
soil a week before planting. 

3. Powdery Mildews — General. White, powdery growth on the leaves, stems, and 
flower petals. Leaves may be killed progressively upwards starting at the base. 
Control: Spray several times, about 10 days apart, using phaltan, Karathane, Acti- 
dione, or sulfur. 

4. Damping-off , Southern Blight, Stem and Root Rots, Wilt — General. Seedlings wilt, 
collapse, and die. Older plants may gradually or suddenly turn yellow, wilt, col- 
lapse, and die due to a rotting of the roots. Water-soaked, white, yellow, or brown 
to black cankers may form at or near the soil line. Other plants may be stunted 
and sickly-looking with decayed roots. A cottony mold may cover infected areas 
at the soil line. Flower spikes pale and wilt. Flowers collapse. Control: Use clean 
seed or treat with Semesan and plant in clean or sterilized soil (pages 437-44) , 
which is well-drained. Treat foxglove seed by soaking in hot water (131° F.) for 15 
minutes. Avoid overwatering and overcrowding. Propagate from disease-free plants. 
Destroy infected plants and 6 inches of surrounding soil. Drench the soil with 
Terraclor 75 (12 ounces per 100 square feet) plus either captan or ferbam (1 
pound) . Indoors, keep water off the foliage and the temperature down. Spray as 
for Rusts (above) . Rotate. 

5. Anthracnose (primarily snapdragon, foxglove, and toadflax) —Round to angular, 
somewhat sunken spots on the leaves and stems. Spots may be pale yellowish-green 
to grayish-white or purplish-brown in color. Numerous black specks may dot the 
centers of the spots. Affected parts or the entire plant may wilt and die. Seedlings 
wilt and collapse. Control: Same as for Rusts and Damping-off (both above). Pull 
and burn severely infected plants when found. 

6. Other Leaf Spots, Blights — General. Small to large spots of various colors, sizes, 
and shapes on the leaves. Centers may drop out leaving shot-holes. Leaves may 
wither and cling to the stem or drop early. Similar spots or cankers on the stems 
may cause rapid wilting and dying. See Figure 165B. Control: Same as for Anthrac- 
nose (above) . 

7. Root-knot — Snapdragon is highly susceptible. See (37) Root-knot under General 
Diseases. 

8. Mosaics (snapdragon, foxglove, penstemon) — New leaves may be puckered, curled, 
and mottled with yellowish or light and dark green areas. Leaves and plants are 
stunted. Control: Destroy infected plants when first found. Malathion or lindane 
sprays control aphids which transmit the viruses. 

9. Verticillium Wilt (snapdragon, foxglove, slipperwort) — Plants wilt slowly or 
suddenly, starting with certain branches. Lower leaves turn yellow at the margin. 
Wilt later progresses up the stem. Greenish-brown to purplish-brown discoloration 
inside the stem near the soil line. See Figure 165A. Control: Rotate. Remove in- 
fected plants together with surrounding soil. Water as little as possible to obtain 
good growth. 

10. Downy Mildew (primarily snapdragon, mullein, and toadflax) —Seedlings and 
young plants stunted, bunchy, dull green, wilt and die from the top down. Older 
plants are stunted. Flowering is reduced. Purplish-gray, mealy, mold patches on 
the underleaf surface and stems in cool, damp weather. Leaves may wither and die. 
Control: Same as for Rusts (above) . 



370 



SNAPDRAGON 




HEALTHY 

Fig. 165. A. Snapdragon Verticillium wilt, B. Blight or stem rot of snapdragon. 



11. Other Nematodes (pin, root-lesion or meadow, stylet or stunt) —Plants lack vigor. 
May be stunted with some dead lower leaves. Feeding roots are stunted and pitted 
with minute, shallow brown wounds. A laboratory examination is needed for 
positive identification. Control: Same as for Root-knot (above) . 

12. Crown Gall (snapdragon) —See (30) Crown Gall under General Diseases. 

13. Ringspot (snapdragon) —Numerous zoned rings of alternating living and dead 
tissue. Whole spots die, then spread and run together with other spots. Whole leaf, 
then entire plant dies. Control: Same as for Mosaics (above) . 

14. Spotted Wilt, Ringspot (snapdragon, foxglove, slipperwort) — Plants may be 
stunted with rosette-like growth. Leaves are distorted. May show yellow, mosaic-like 
patterns. Flowers may be marked with pale red or yellow rings. Thrips transmit the 
virus. Control: Same as for Mosaics (above) . Use DDT and malathion to control 
thrips. 

15. Aster Yellows, Curly-top (foxglove, monkeyflower, toadflax) —See (18) Yellows 
and (19) Curly-top, under General Diseases. Leaves are curled and dwarfed. 
Plants become stunted and bunchy. Leafhoppers transmit the viruses. Control: 
Same as for Spotted Wilt (above) . 

16. Flower Blight — See under Chrysanthemum, and (31) Flower Blight under General 
Diseases. Control: Same as for Gray-mold Blight (above) . 

17. Leaf and Stem Nematode (butter-and-eggs, foxglove, monkeyflower, slipperwort, 
toadflax) —Angular brown blotches on the leaves limited by the veins. Control: 



SNOWBERRY 371 

Keep water off the foliage on indoor plants. Outdoors, apply a dry mulch to keep 
water from splashing on the leaves. Pick off and burn infested leaves. Burn tops in 
the fall. Rotate. 

18. White Smut (butter-and-eggs, collinsia) —See (13) White Smut under General 
Diseases. 

19. Black Mildew (penstemon) —See (12) Sooty Mold under General Diseases. 

SNEEZEWEED — See Chrysanthemum 

SNOWBALL -See Viburnum 

SNOWBELL - See Silverbell 

SNOWBERRY [COMMON, MOUNTAIN, ROUND -LEAF], CORALBERRY or 

INDIAN CURRANT, CHENAULT'S CORALBERRY, WOLFBERRY, 

WAXBERRY (Symphoricarpos); ABELIA [ CHINESE, GLOSSY ] (Abelia); 

HONEYSUCKLE [AMUR, BELLE, BLUE -LEAF, BOX, CLAVEY'S DWARF, 

CORALINE, EUROPEAN FLY-, FLY-, FRAGRANT or WINTER, HALL'S, 

JAPANESE, JAPANESE PINK, MORROW, PRIVET, STANDISH, 

SWAMP FLY-, TATARIAN, TRUMPET, WINTER, YELLOW], 

WOODBINE (Lonicera); ELDER [AMERICAN or SWEET, BLUEBERRY, 

EUROPEAN, EUROPEAN RED, GOLDEN, GOLDEN EUROPEAN, 

RED - BERRIED, SCARLET ] (Sambucus); WEIGELA [ CRIMSON, 

ROSE] (Weigela) 

1. Leaf Spots, Anthracnose, Scab or Spot Anthracnose — Widespread. Spots of various 
sizes, shapes, and colors appear on the leaves. Leaves may become distorted, wither, 
and drop early. Spots may also occur on the stems, berries, and flowers. Berries 
shrivel and dry up. Twigs may die back several inches. Control: Destroy infected 
plant parts. Cut diseased snowberry stems to the ground and burn in the fall. Apply 
zineb, captan, ferbam, dichlone, or fixed copper at 7- to 10-day intervals from when 
the buds swell to just before bloom. Phenyl mercury is effective against Anthrac- 
nose. Follow the manufacturer's directions. 

2. Berry Rots (snowberry, coralberry) — Widespread. Pink, purple, yellowish, brown, 
or black spots on the berries. Fruit may become soft, watery, rotted, and covered 
with a gray or black mold. Or berries may shrivel, dry, and "mummify." Control: 
Spray as for Leaf Spots (above) . 

3. Cankers, Twig Blights, Dieback — Twigs die back. Often caused by rough, girdling 
cankers on the twigs and branches in which coral-pink to black "pimples" may 
be embedded. Control: Prune out and burn affected twigs and branches. Spray as 
for Leaf Spots (above) . 

4. Honeysuckle Leaf Blight — Widespread. Irregular, yellowish-green areas in the 
leaves which soon turn tan and finally a brownish-black. A whitish "bloom" is often 
evident on the underleaf surface. Leaves roll, twist, wither, and fall early. Only 
young leaves are infected. Control: Same as for Leaf Spots (above) . Dwarf type 
may be resistant. 

5. Rusts — Small, yellowish or brownish pustules on the upper leaf surface with orange 
"cluster cups" on the underleaf surface. Alternate hosts may include various wild 
and lawn grasses, or sedges (Carex spp.) . Control: If serious, apply zineb or fer- 
bam as for Leaf Spots (above) . 

6. Collar Rot, Trunk Canker, Wood or Heart Rots — Plants sickly. Die back from a 
rot at the soil line. A canker may form on the trunk. Control: See under Dogwood, 
and (23) Wood Rot under General Diseases. 



372 SNOWDROP 

7. Powdery Mildews — General. White, powdery mold on the leaves and stem tips. 
Tips of shoots may die back. Snowberry leaves may be distorted. Control: Spray 
with sulfur, Karathane, or Acti-dione several times, 10 days apart. 

8. Crown Gall and Hairy Root — Rough, irregular, swollen, cauliflower-like galls on 
the stem at or near the soil line. Plants may appear sickly. Control: Dig up and 
burn affected plants. Do not replant in the same soil for 3 years. Avoid injuring 
plants when cultivating or mowing. Plant disease-free stock. 

9. Stem Gall (snowberry, coralberry) — Numerous, small galls may girdle the stems. 
Parts above the galls may die. Control: Prune out and burn affected parts. Spray 
as for Leaf Spots (above) . 

10. Verticillium Wilt (elder) —See (15B) Verticillium Wilt under General Diseases. 

11. Root Rots — See (34) Root Rot under General Diseases. May be associated with 
root-feeding nematodes (e.g., dagger, lance, pin. ring, root-lesion, spiral, stem or 
rot, sting, stunt or stylet) . 

12. Root-knot — Weigela is very susceptible. See under Peach, and (37) Root-knot un- 
der General Diseases. 

IS. Leaf Scorch (primarily golden elder) —Leaves are scorched where unusually hot 
and windy. Control: Plant in a more protected location. Water thoroughly during 
hot, dry periods. 

14. Chlorosis — In alkaline soils. See under Maple. 

15. Web Blight, Thread Blight (elder, honeysuckle) —Southeastern states. See under 
Bean and Walnut. 

16. Gray-mold Blight — See (5) Botrytis Blight under General Diseases. 

17. Infectious Variegation (honeysuckle)— Leaves mottled green and yellow with the 
veins yellow. See (16) Mosaic under General Diseases. 

SNOWDROP -See Daffodil 

SNOWDROP -TREE -See Silverbell 

SNOWFLAKE - See Daffodil 

SNOW - ON - THE - MOUNTAIN - See Poinsettia 

SOAPBERRY [ CHINESE, FLORIDA, SOUTHERN, WESTERN ] (Sapindus) 

1. Leaf Spots, Leaf Blight — Small to large, spots and blotches of various colors on 
the leaves. Control: Collect and burn fallen leaves. Prune to keep shrubs and trees 
pruned out. Spraying with captan or zineb during rainy periods should be bene- 
ficial. 

2. Canker, Dieback — Twigs die back from discolored, girdling cankers. Control: 
Prune out and burn affected parts. Otherwise same as for Leaf Spots (above) . 

3. Powdery Mildew — Grayish-white, powdery mold growth on the leaves. Control: 
If serious enough, apply two sprays, 10 days apart, using sulfur or Karathane. 

4. Root Rot — See under Apple, and (34) Root Rot under General Diseases. 

5. Mosaic — See (16) Mosaic under General Diseases. 

6. Mistletoe — See (39) Mistletoe under General Diseases. 

7. Thread Blight — Southeastern states. See under Walnut. 

SOAPWEED-See Yucca 
SOLANUM — See Potato and Tomato 



SPEEDWELL 373 



SOPHORA - See Honeylocust 

SORBUS-See Apple 

SORRELTREE, SOURWOOD (Oxydendrum) 

1. Leaf Spots, Purple Blotch — More or less round to irregular, dull red, brown, or 
purple blotches on the leaves. Centers of spots may later turn brown and dry.